Research into the impact of substitutes in professional football on physical and technical performance | BMC Sports sciences, medicine and rehabilitation

The current study aimed to (1) quantify the physical and technical profile of substitutes, substitutes and players who completed the entire match, taking into account situational variables; (2) analyze the physical and technical performance difference between substitutes and players who substituted or completed the entire match at each playing position. Previous studies have mainly examined the physical performance of substitutes in football [5, 18,19,20,21]but only a few have examined the technical performance of replacements [5, 19]. In the current study, more comprehensive and detailed technical indicators were analyzed to investigate the impact of substitutes on technical performance. The results of the current study showed that substitutes performed better in terms of physical performance (Table 3), especially at high-intensity running and sprint distances, than players who were substituted or completed the entire match. The findings have shown the similarity with previous studies as the better physical performance of substitute players [5, 19]. Substitutions are generally used to reduce the impact of fatigue and maintain a high level of running performance for the entire team [34]. High-intensity running distances seem to be a particularly essential and useful indicator of physical performance in football [35], and the findings of the current study showed the significant difference in high-intensity running distance between substitutes and players who are substituted or complete the entire match. However, replacement players perform worse on the total distance than replaced players. Accordingly, playing time on the field is the most important factor that influences match intensity [36]. Replaced players mainly play on the field in the first half and would be replaced in the second half [5]. During the playing time of substituted players, the match intensity may therefore be higher than that of substitutes playing on the field, resulting in substitutes showing a lower total distance. Depending on playing positions, substitutes from all positions exhibit higher high-intensity distance and sprint distance than substitute players or players who complete the entire match. The finding is similar to the results regardless of positions. However, substitutes in the wide midfield show lower total distance than replaced players and players have completed the entire match. Coaches would introduce more defensive players to strengthen the defense if the team wins [4]. Modric, verse [37] It was found that wide midfielders’ total running distance decreased and sprint distance increased in the defensive phases, which is in line with the findings of this study.

By focusing on technical performance, technical indicators in a broader range were analyzed and performance related to scoring, passing and defending was quantified (Table 1). Despite the importance of technical performance, little literature focuses on the technical activities of substitute players [1, 5, 19]. Bradley, Peñas [5] first analyzed the technical activities of substitutes, but found no significant difference in passing activities between substituted players and players who completed the entire match. The results of the current study show that substitutes mainly perform better in shooting activities and defensive activities, while they exhibit poorer passing activities, including passing, passing accuracy and long passes, than players who substituted or completed the entire match (Fig. 1). Existing literature mentions passing activities such as short passes; successful passes decrease from the first to second half of football matches, which can be affected by fatigue [38]. According to the theory, it is a good strategy for the coach to make substitutions on the field to counteract the decline in the team’s technical performance. Additionally, match status also impacts player performance as replacement players may attempt riskier passes and crosses due to the match status when they were introduced onto the pitch. [39]. Furthermore, research into substitution introduction patterns shows that coaches would introduce more players into attacking positions in the second half of the match [5]. Thus, substitutes would engage in riskier and more attacking activities when coaches aim to change the score line, causing the substitutes to employ lower passing accuracy but perform more attacking activities, including shots, shots on goal, key passes and breakthroughs.

One of the most compelling findings in time-motion analysis research is the significant differences between all playing positions in physical performance [6,7,8, 40,41,42] and technical performance [5, 24, 43, 44] of top footballers. Therefore, it is crucial to discuss the performance differences between players who are substituted, replaced and completed the entire match for each playing position. According to this research, substitute centre-backs have shown lower passing and organizational activities, while performing more defensive actions. To win the game, coaches usually send the defenders onto the field when their team is ahead [16, 17]. Thus, the tactical objective of substitute central defenders and full-backs is to defend the opponent’s attackers and protect the attacking third zone. Under the tactical objective, substitute defenders (center defenders and full-backs) would perform lower passing actions and higher defensive actions compared to players who substituted or completed the entire match. Furthermore, to strengthen the defensive level, attacking players may also have been introduced on the pitch in a defensive role, to hold the scoreline or waste time during the final stages of the match. [1]. These may be the reasons why attacking substitutes, such as forwards and wide midfielders, have shown more tackles, clearances and pass blocks than players who have been substituted or played out for the entire match.

On the other hand, the current research has shown that substitute strikers and wide midfielders demonstrate better passing and organization actions, such as passing, ball controls, crosses, short passes and long passes, than players who were substituted or completed the entire match. Players with attacking playing positions are usually introduced onto the field when their team is losing [1, 16, 17]. In general, replaced players are more likely to be considered underperforming if the team loses [17]and coaches introduce attacking substitutes to create more scoring opportunities and improve the performance of the entire team [5, 39]. The higher passing and organizational performance of attacking substitutes than those who have been substituted or completed the match are considered crucial factors for the success of the match. [5, 24, 39, 45]. Furthermore, substitute central midfielders in this study showed more scoring actions. Research into elite French football has shown that the increased number of goals scored by substitutes was a factor in distinguishing successful teams [46]. Therefore, substitute central midfielders can be introduced onto the pitch as another attacker to score a goal when their team is losing. These may be reasons why replacement central midfielders have a lower passing performance than replaced players and complete the entire match. Furthermore, a very interesting result from the current research is that substitute full-backs perform more shots, which is more likely the attacking playing style. Although coaches introduce some players with defensive positions, such as fullbacks, the introduced players may play in the attacking playing position in an attempt to create scoring opportunities. [19].

Overall, substitutes can indeed improve the physical and technical performance of the team. The current study has confirmed previous findings as substitutes are introduced to change the scoring line or reduce the influence of fatigue [1, 4, 5, 16, 17, 19, 39, 47]. By taking into account the situational variables, the current study analyzed a wider range of technical variables and quantified the technical performance of substitutes in different playing positions. Furthermore, the match location influences most technical performance indicators, which show higher scoring and passing performance, while defensive performance is lower. The findings verified home field advantage and confirmed previous research [26, 31].

However, some limitations need to be further studied in subsequent research. Sports psychology literature shows that substitutes may perform worse when introduced into the match as starters due to the psychological strain [48]. It is important to investigate the performance difference of substitutes between the substitution situations and the starter situation. Furthermore, the timing of substitutes introduced onto the field also influences performance, as the match status determines the tactical purpose of substitutions. [5, 16, 17]. In the current study, the match data was analyzed for only one year and the substitution option was changed in 2020. To better investigate the influence of substitutes on match performance, it is important for future research to analyze match data over a larger number of seasons.