Many of us will remember the 2014 World Cup final in Rio de Janeiro, when German player Mario Götze came on as a substitute to score an 113^th minute winner against Argentina. Likewise, more recently in Qatar 2022, Dutch coach Louis van Gaal introduced Wout Weghorst and Frenkie de Jong to bring his team to life against Argentina. Weghorst’s goal came in the final touches of normal time, keeping the team’s hopes alive for extra-time.

Although the match progressed to penalties, penalty scorers for both teams included players who had started the game on the bench. Similarly, it was Bruno Petković, who came on the pitch after 72 minutes in his game for Croatia against Brazil, that clawed his team back into the competition. He scored an equalising goal during the 117^th minute to take the match to penalties, and ultimately, to take Croatia to the semi-finals.

The effective use of in-game substitutes is nothing new, starting officially in men’s international football in the 1954 World Cup when Richard Gottinger replaced Horst Eckel for West Germany. However, it wasn’t until the 1965 season when this rule was introduced into domestic football. Even then, to regulate their use, only one substitution was permitted in the event of injury to a player. The rules further advanced so that each team was permitted three substitutes per game, rising to four if extra-time was needed, regardless of injury.

Beginning in 2022, for the first time in the history of the World Cup competition, managers were allowed to make five substitutions over the 90-minute match, rising to six for extra-time. In addition, we have also seen the introduction of concussion protocols, meaning that in the event of a head injury, teams are allowed to make yet another substitution. It is therefore possible (if not probable) that over half of the starting squad may have been swapped out and replaced by the time a match ends. From injury replacements to impact players, the era of the super-sub has well and truly begun.

Naturally, with a shift in how substitutes are used during a match (and how many), the performance impact of this bespoke population of players has come into the spotlight. Sports scientists now have the task of unpicking the demands placed on these players to discover how best to optimise their role within the team. This is an area of interest that has already been undertaken by researchers at Leeds Trinity University.

Between 2017 and 2020 research staff at Leeds Trinity worked with a professional soccer team to develop an understanding of the matchday activities of partial match players. Intuitively, on matchdays, substitute players had much lower physical demands relative to their starting counterparts.

However, it soon became apparent that due to different pre-pitch entry practices, room for improvement existed within the activities that were undertaken before substitute players entered the field of play. One side effect of this was possibly that the effects of warming up had worn off by the time they entered the pitch. In fact, in a separate study, a “re-warming-up effect” was observed for substitutes during their first 10 minutes on the pitch. This is understandable, as substitute players, on average, didn’t enter the pitch until at least 75 minutes after they had finished the initial warmup.

On matchdays it may be impractical to conduct traditional warmups and re-warmups with substitute players because of several factors. In most domestic tournaments, coaching and performance staff are restricted to the technical area during match play, so a challenge of effectively supervising substitute players during their re-warmups exists. Unless, of course, there are other ways that substitute players may remain warmed up. That is now the question posed by researchers at the University, in the hope that they can uncover practical, yet effective, strategies to maximise the output of these increasingly vital players.

Natalie Smith is a part-time postgraduate researcher at Leeds Trinity University and is conducting her research under the supervision of Professors Mark Russell and Martin Barwood, who lead the Enhancing Human Performance research theme in the Faculty of Social and Health Sciences. Natalie’s research will seek to continue the investigations into the preparatory strategies of partial-match team sports players.