## 1 Introduction  
Modern football has evolved into a sport where matches are increasingly physically demanding, causing greater stress on football players [1]. A previously published study has shown that between the 2006/2007 season and the 2012/2013 season, the high-intensity and sprinting demands on football players increased by 30% and 35%, respectively [2]. A study conducted comparing the seasons 2014/2015 and 2018/2019 also found a notable increase in the total distance covered, distance covered at high intensity, and sprinting [3]. The growing trend of increments in running demands in football is so significant that some authors predict that by the year 2030, matches could become 40% more demanding in terms of high-intensity activity [4]. Although other authors argue that these increases will be more moderate, with high-speed efforts expected to rise by around 10% and sprint distance covered by 15% [3], it seems evident that the physical demands on football players are increasingly stringent. Football players face greater physical demands due to more intense matches, and another hallmark of modern football is that players participate in more matches per season, exposing themselves to more frequent and dense periods of high-intensity effort [4; 5; 6]. Taking into account the broader context, an increase in the number of substitutions per match could emerge as a viable strategy for mitigating injury risks, particularly in tightly scheduled matches [7; 8]. This approach would be especially pertinent for players exposed to high chronic competitive loads [9]. A higher number of substitutions could also potentially counteract the observed decline in running performance during the second half of football matches, which could be reflected in matches that are more attractive for spectators. In 2021, in response to the COVID-19 pandemic and to minimize match overload and potential player fatigue, the Federation Internationale de Football Association (FIFA(r)) authorized an increase to five substitutions for each team per match, instead of the usual three. This new regulation caused a change in football, affecting coaches' decision-making, particularly in everything related to substitute players. Although football coaches generally adhere to similar substitution patterns [10] and substitutes are typically introduced at halftime or during the second half of the game [9; 11], the reasons for substitutions vary widely. For example, tactical adjustments, countering fatigue, reshaping the team after dismissals, replacing cautioned players, addressing injuries or under-performance, granting playing time to those with fewer minutes, and preventing fatigue accumulation among team members are all factors that influence substitution decisions [9; 11; 12]. Despite the existence of different reasons for which substitutions are made, the physical response of substitute players is the most studied element in the literature. [PERSON] et al. (2023) demonstrated that in the Australian National Premier League (semi-professional) and National Youth League (youth professional), while starting players accumulate a higher absolute amount of total distance covered and high-speed running distance, substitute players, across all playing positions, exhibit a greater relative high-speed running distance per minute compared to players who participate throughout the entire match [13]. Similarly, a study of the English Premier League also found that substitute players tend to cover a greater distance with high-intensity running during the equivalent time period compared to starters [12]. In addition, substitutes were found to accumulate significantly longer distances of high-intensity running and sprinting during the last 15 min of the match compared to players who played the entire match [14]. Despite the research conducted to understand substitute players, investigations of the impact of the new regulations that have expanded the maximum number of substitutions on teams' physical performance have not been carried out.