Comparative of the goals scored by set pieces during the Eurocup and Copa America 2021

Diego Muriarte Solana

Francisco Gallardo Mármol

Ignacio Grande Rodríguez

Manuel Barba Ruiz

Juan Hernández Lougedo

Adrián Martín-Castellanos

Abstract

This study aimed to establish a comparison between the goals scored from set pieces (corners, direct and indirect free kicks) in the European and South American (EURO 2021 – COPA 2021) competitions, coinciding within the same time frame. For this purpose, all goals (22 and 17, respectively) were analysed and variables related to the following different action phases were collected: beginning (kicker’s foot, minute, starting area), development (marking, ball trajectory, number of attackers or defenders) and the end (height of the previous pass, number of passes or contacts before the goal). A Cohen’s kappa and the Intra-class Correlation Coefficient were per-formed between two observers, and an analysis using Chi-square and Mann Whitney U was carried out. The results showed no significant differences, except for the height of the pass (with a higher-than-expected number in the medium pass and COPA) and the confederation of the club to which the scoring player belonged (a higher percentage of players scored from UEFA in EURO, and CONCACAF in COPA). These findings could suggest a European influence in set-pieces due to recent success in international competitions and could be useful for coaches and analysts to expand the information about rivals.

Introduction 

Set pieces have clear importance in football development in recent years as one of the trends accounted for in team performance analysts (Sarmento et al., 2018). The technical-tactical behaviours associated with some of the categories belonging to this variable have evolved through differences in the importance of each variable in different editions played, such as the type of offensive organisation, the transcendence, or the number of attackers involved in the play (Maneiro et al., 2021). In the existing literature, studies have focused on analysing different competitions to clarify different questions, such as which type of defence presented more favourable results or whether the effectiveness of the actions increased by getting more players in the team in contact with the ball, or through the trajectory of the ball (Casal et al., 2015; Kubayi & Larkin, 2019).

Set-pieces are a fairly common occurrence on the field, consuming around 38% of the total match time (Siegle & Lames, 2012). Several studies estimate that between 30 and 40% of goals scored by teams come from set pieces (Casal et al., 2015; Kubayi, 2020). González-Rodenas et al. (2020) point out that 24.1% of UEFA Champions League goals in the 2016-2017 season were scored from set pieces, highlighting that the technical-tactical actions that achieve a goal and their spatial characteristics are related to the type of defence used by the opposing team, which is why authors such as Rumpf et al. (2017) extol its relevance. The average number of corners per game is between 10 and 11 (Sainz de Baranda et al., 2011) and, despite their low effectiveness (2.2% following Casal et al. [2015]; 3.6% in Lee & Mills [2021]), this type of action can be decisive for the outcome of the match (Casal et al., 2015; Maneiro Dios et al., 2019).

Regarding free kicks, López-García et al. (2018) found an average of 31.42 free kicks per game. Although free kicks had a similar low effectiveness as corner kicks (3.1%), high-lighting these actions, the number of attackers involved, the delivery and the offensive organization could be important indicators to consider improving the scoring ratio. Link et al. (2016) valued density, type of barrier, distance and the number of players as important variables highly dependent on space, while also highlighting centrality and proximity to the goal as factors that increased these variables. About the defensive organisation in these actions, it was found that those teams defending corners using zonal marking conceded more goals compared to a combined model, and that, by placing a defender at each of the posts, no goals were conceded by the defending teams.

Due to its importance, different research has been carried out in both national and international competitions. This type of action has not only been studied in men’s football but also in women’s football, showing that it is key to winning or drawing matches and that the executions are similar (Maneiro Dios et al., 2019).

Although a widely studied field, it is rare to find comparisons between international competitions in the published literature. The research focused on this comparison finds that the passing networks before scoring a goal are similar in both continents (McLean et al., 2017).

For this reason, and to establish a comparative line of research between these two competitions, we have taken advantage of the simultaneity of tournament development to analyse whether there are different patterns or associations in the goals scored from set pieces between a European international competition (EURO 2021) and a South American competition (COPA 2021), thus proposing a new line of research.

Materials and Methods

Sample

For the analysis of these actions, all goals scored from direct free kicks, indirect free kicks and corner kicks in the final phases of the EURO 2021 and COPA competitions were collected, with a total of 22 and 17 goals scored respectively. A total of 51 EURO 2021 matches, and 39 COPA matches were watched. Both tournaments took place between 11 June and 11 and 10 July 2021, respectively. Penalty kicks, centre kicks and throw-ins were excluded from this study because the structure is similar for direct, indirect and corner kicks; in penalty kicks there is no defence and the percentage of goals from goal kicks and throw-ins is low, although they occur frequently (Siegle & Lames, 2012; Stone et al., 2018). 

Procedure 

Set pieces were analysed by systematic observation according to Lames (1994) and Singer and Willimczik (2002). Two professionals in sport sciences with more than 10 years of experience in the area oversaw the recording, visualised all the actions, and were trained to provide an accurate and reliable data recording.

Although the analysis of these actions was carried out independently, a total of four meetings were held to define the variables and understand each situation. To achieve this, less than 15% of the sample was used in the meetings.

Variables  

To set the variables, several studies were considered (Sainz de Baranda et al., 2005; Di Salvo et al., 2007; Sainz de Baranda et al., 2011; Casal et al., 2015; Link et al., 2016;  Fernández-Hermógenes et al., 2017; Beare & Stone, 2019; Kubayi & Larkin, 2019; Wang & Qin, 2020; Lee & Mills, 2021; Maneiro et al., 2021). Those previously used in different studies of set pieces had been taken and adapted, adding other indicators used for patterns of play and scoring research in both international and national competitions. The categorical variables are shown in Table 1.

Table 1

Description and categorisation of the nominal variables used for the study.

See Table

Table 2 presents the definition of the numerical variables that have been collected for this study.

Table 2

Description of the numerical variables used in the research.

See Table

Figure 1

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Figure 2 (left) and 3 (right)

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To establish common criteria for the zones, a modified categorisation from previous studies was used (Beare & Stone, 2019; Lee & Mills, 2021; Wang & Qin, 2020). The register was used for the right or left zone according to the scenario of the kick around the central zone, and the penalty spot and the central point of the field were used as references (Ardá et al., 2014), as shown in Figure 3.

Statistical analysis

As with the analysis, the methodology applied in this study was similar to González-García et al. (2016). Cohen’s kappa coefficient (k) was used to determine the degree of agreement between observers on nominal or categorical variables, and the following criteria was used to determine interpretation: 0 – .2 Poor agreement; .21 – .40 Fair agreement; .41 – .60 Moderate agreement; .61 – .80 Good agreement; .81 – 1 Very good agreement (Altman, 1991). These variables are expressed using the frequency of observation.

For those continuous variables, expressed as mean and standard deviation (M ± SD), the standardised typical error, the intra-class correlation coefficient (ICC), and Pearson’s r  were calculated using the Hopkins’ spreadsheet (2015). To classify ICC, criteria established by Koo and Li (2016) was followed; <.5 Poor reliability; .5 – .75 Moderate reliability; .75 – .9 Good reliability; >.9 Excellent reliability.

Cohen’s kappa and ICC values are shown in Table 3.

Table 3

Cohen’s kappa and ICC for all variables.

See Table

The normal distribution of the variables was checked using the Shapiro-Wilk test. The Mann-Whitney U test was used to compare numerical variables, such as seconds, number of players involved, touches, barrier, and number of passes by the tournament. In parallel, the relationship between the different nominal variables and tournament was observed using Pearson’s Chi-square test, with Fisher’s Exact Test.

To calculate the size effect, Cramer’s V was the measure used for Pearson’s Chi – square, following Rea and Parker (1992), with the following interpretation: <0.1 = Negligible association; ≥ .1 to < .2 = Weak association; ≥ .2 to < .4 = Moderate association; ≥ .4 to < .6 = Relatively strong association; ≥ .6 to < .8 = Strong association; ≥ .8 to 1 = Very strong association.

The level of significance was set at .05. The collected data were studied using the software Statistical Package for the Social Science (SPSS, IBM Corporation; Armonk, New York, USA), in version 25.0.

Results

In most cases, no significant differences were observed between the qualitative variables. A relatively strong association was found between the height of the previous pass and the tournament, with the number of passes at an average height higher than expected by chance in COPA 2021; in EURO 2021 the same figure was lower than expected (Table 4).

Table 4

Comparison of nominal variables between EURO 2021 and COPA 2021.

See Table

In addition, a relatively strong relationship was also observed between the confederation of the scoring player and the tournament. The percentage of scoring players belonging to a UEFA club was higher than expected in EURO 2021 when compared to COPA 2021, while COPA 2021 recorded a higher-than-expected number of scoring players belonging to CONCACAF when compared to EURO 2021. No differences were found for players belonging to AFC or CONMEBOL clubs in the tournaments.

Regarding the numerical variables, no significant differences were found depending on the competition analysed (p > .05) (Table 5).

Table 5

Comparison of quantitative variables between EURO 2021 and COPA 2021.

See Table

Discussion

After an analysis of the variables collected in this study that accounted for the development of these set pieces, no significant differences were found in the comparison between the Copa America and the European Championship, except for the height of the pass received by the player and the confederation to which the scoring player’s club belongs. These findings could align with Wilwock and Furtado (2019), where no substantial differences were found between Euro 2016, Copa America Centenario 2016 and the 2017 Confederation Cup; however, this analysis takes into account all goals scored by teams, not only those scored from set pieces.

It is worth noting that although a higher-than-expected number of players with clubs belonging to the UEFA confederation were randomly registered for EURO 2021, which would be logical given that they belong to the continent, the same was not observed for CONMEBOL players. This could be related to the influence or impact of the European style of play, which has dominated international competitions for much of the last decade. For example, European teams have won the FIFA World Cup uninterruptedly from 2006 to 2018 (FIFA, 2021). Regarding the FIFA Club World Cup, Europe has also been the tournament leader since its inception, and the UEFA confederation has won 13 titles, compared to CONMEBOL’s four (FIFA, 2021). This fact could be a determining factor in the teams’ execution of similar models or actions of play. However, a more in-depth study should be carried out on the historical development of Latin American and European teams over time to confirm this hypothetical influence, given that research focused on this comparison determines that there are similar styles between the football passing network before scoring goals on the American and European continents (McLean et al., 2017).

Another possible explanation for these results, and one of the limitations of the study, could be the lack of a larger sample. With only successful set-pieces, and in competitions of short durations, the number of actions counted was small. One of the alternatives to alleviate this deficit could be to limit the time frame and acquire a larger sample with a collection of data from different championships.

Regarding the contrast of the data from our research with other studies, it is difficult to establish similarities due to the scarcity of similar scenarios occurring in the same year and period. A comparison could be drawn with the study of Prieto-Lage et al. (2021), which analyses corner kick behaviour in different European leagues. Although there are differences in the conceptualisation of the variables (for example, only attackers or defenders inside the area in the first contact are counted), can also be found in the same study that European teams usually attack with more than four players, and it is frequent in leagues such as the English, Italian and German leagues that attack with more than six players. Further, there are more than six players in the defence area; we found an average of 10.64 players in Europe, accounting for those players located close to the area.

It is also worth noting the contrast between previous studies that indicates that the second half is key to the achievement of these actions in the competitions of both confederations. While the European competition does register these standards, similar to the Spanish and German leagues, in the South American competition could be found a similardistribution between the first and second half (Prieto-Lage et al., 2021), unlike in regular club competitions in this region. This differs from what is reported in the Spanish and German leagues (Carelli et al., 2016). The distribution of the first and second halves differs from that reported by the authors in the study of other national and international competitions (Casal et al., 2015; Junior, 2015; Njororai, 2014; Prieto-Lage et al., 2021).

Regarding the completion and initiation of these actions, it is difficult to establish comparisons with other studies (Beare & Stone, 2019; Link et al., 2016; Prieto-Lage et al., 2021) by modifying and adapting the observation graph that has been used in this research from Lee and Mills (2021), according to the side on which the stationary ball was located. Finally, emphasising the relevance of these actions, it could be determined that a low number of set-piece goals presented a direct impact on the final result, although this could be due to the conceptualisation of the variable (Ardá et al., 2014; Casal et al., 2014, 2015; Maneiro Dios et al., 2017).

Among the future lines of research that could be added to the study of these types of actions in competitions, it could be analysed whether the time differences suffered by the teams when competing in different locations, within the same competition, could influence these behaviours and their effectiveness.

Another possible line of research could be the study of the influence of playing as a “host” of the competition or as an away team, similar to studies that analyse the relevance of playing as a home team in this type of tournaments.

Conclusions

The goals scored from set pieces (direct kicks and corners) in the European Championship and the Copa America did not show any differences, except for the height of the pass received by the player and the conference of the club to which the player scoring the goal belonged. These findings are in line with the few studies previously conducted on this comparison. The small sample size and the European dominance in international competitions could affect these results, so the line of research must be continued in order to assess potential reasons for these results.

The use of this information for coaches and performance analysts can help explore similarities between teams from different confederations, broadening the information at hand regarding the development of these actions, and establishing key points for operational strategy in matches or championships.