Trent Alexander-Arnold's Champions League debut for Real Madrid was cut short due to a hamstring injury sustained early in the match against Marseille. The incident occurred just three minutes into the game at the Santiago Bernabéu, with Alexander-Arnold pulling up after making a pass and immediately feeling discomfort in his left hamstring. He was then assessed by the medical staff and subsequently replaced by Dani Carvajal in the fifth minute.

The injury is a significant blow for Alexander-Arnold, who had only made three starts for Real Madrid this season. He had been given a brief eight-minute appearance against Real Sociedad in preparation for the Champions League match, but even that additional rest was not enough to prevent the injury. Visibly upset after being substituted, Alexander-Arnold's injury also casts doubt on his participation in upcoming international matches for England in October and November. He had previously been left out of the England squad earlier in the month.

Real Madrid is already facing an injury crisis, with Ferland Mendy, Antonio Rüdiger, and Endrick also sidelined. Additionally, Dean Huijsen is serving a two-match La Liga ban. The return of Jude Bellingham and Eduardo Camavinga from their respective injuries does provide some relief for the team. The club is awaiting an update on the severity of Alexander-Arnold's injury.

The injury also jeopardizes Alexander-Arnold's potential return to Anfield to play against his former club, Liverpool, in the Champions League on November 4. This match was highly anticipated, as it would have been his first game back at Liverpool since his transfer to Real Madrid.

Dani Carvajal, who replaced Alexander-Arnold, is an experienced player with six Champions League titles to his name. He had already been in good form, starting in the recent 2-1 win against Real Sociedad. Real Madrid will now rely on Carvajal's leadership and experience as they navigate their Champions League campaign and other competitions amidst the ongoing injury concerns. Both Real Madrid and Liverpool are aiming to progress through the competition and qualify for the knockout stages automatically.