If it weren't for the last-minute goal conceded, Manchester City would have welcomed a long-awaited big win. In the 20th round of the Premier League against West Ham United, it was their first time in recent weeks to achieve two consecutive victories, with City's points reaching 34, and the team's form looking to be improving. However, it is somewhat regrettable that City ultimately failed to keep a clean sheet, conceding a goal in the 71st minute, resulting in a 4-1 outcome. And all this began with Guardiola's two substitutions. Guardiola brought on Gundogan and Walker in the 61st minute when the team was already leading by four goals. Their entry did not continue City's good form but instead gave West Ham United an opportunity. Gundogan's current ability to intercept in midfield has significantly declined, and Walker's speed can no longer be his greatest advantage. Just three minutes after coming on, Walker received a yellow card for a foul, giving the opponent a well-positioned free-kick from which Paqueta almost helped West Ham United change the score. Ten minutes after Walker and Gundogan came on, City's midfield was completely penetrated by three passes from West Ham United. Walker's defensive speed did not pose much of a restriction to the opponents, and Soucek's pass allowed Firkruge to make a central run and change the score. This goal conceded saw neither Walker nor Gundogan play their roles effectively, and the mentioned goal conceded and yellow card were just a microcosm of their entire game, especially Walker, whose role at City has clearly diminished, and…