Real Madrid right-back Trent Alexander-Arnold was forced off against Marseille in the Champions League with what appeared to be a hamstring injury.
Los Blancos emerged as 2-1 winners in their first Champions League game of 2025-26 on Tuesday, overcoming the fact they had been reduced to 10 men in the 72nd minute when Dani Carvajal was sent off.
The right-back was brought on in the fifth minute of the match for Alexander-Arnold, who held the back of his leg and received treatment before being replaced.
Alexander-Arnold's substitution will come as a serious blow to boss Xabi Alonso, who could face the prospect of being without his two first-choice options on the right side of defence for multiple games in Europe.
The defender's injury could also rule him out of his side's clash against former club Liverpool on November 4, though much will depend on the severity of his issue.
How long could Alexander-Arnold be out for?
When Bukayo Saka suffered a hamstring injury in late December 2024 for Arsenal, he did not return to the pitch until April 1, 2025.
If Alexander-Arnold's apparent muscle issue is a grade three injury, then recovery could take a minimum of eight weeks, and surgical intervention may be required.
There is a chance that the 26-year-old only felt a mild strain, and players have returned to action within a couple of weeks.
The right-back could also have suffered a partial tear of the muscle or tendon, and such an injury would typically require three to six weeks on the sidelines.
Are Alexander-Arnold's injuries becoming a concern for Xabi Alonso?
Alexander-Arnold established himself as a regular in Liverpool's first XI in the 2017-18 season at just 18 years old, but there is a fear that his early start has led to more frequent injuries in recent seasons.
The Englishman has suffered eight separate injuries since the 2023-24 campaign, and his latest setback would be his fourth hamstring injury in that same period.
He was sidelined with two hamstring issues in 2024-25, as well as an ankle problem, and he was subsequently unavailable for 64 days.
Alexander-Arnold was not selected in Thomas Tuchel's England squad for the September international break, and he faces the prospect of missing out on the squad entirely for the 2026 World Cup if he continues to be plagued by injuries.