Walker and Maguire were both named in the starting lineup for Saturday's clash with Brazil, where Endrick condemned England to their first Wembley defeat since October 2020.
The former's race was run with just 19 minutes on the clock, though, as he tried to play through the pain of an apparent hamstring problem before coming off for debutant Ezri Konsa.
Head coach Gareth Southgate was in the dark about the severity of Walker's issue immediately after the game, although the Manchester City man was hopeful that he had not sustained anything major.
However, ahead of Manchester City's pivotal Premier League clash with title rivals Arsenal on March 31, Walker has now pulled out of the squad and will play no part in the Three Lions' upcoming battle with Belgium.
England confirmed that Walker would continue to receive assessment upon his return to Manchester, but his participation in the showdown with Arsenal on Easter Sunday has now been plunged into even more doubt.
The 33-year-old is one of three players to leave the camp owing to recent injuries, a list which also includes Manchester United's Maguire, who took the captain's armband from Walker upon his teammate's exit on Saturday.
Maguire was substituted with 67 minutes on the clock against Brazil, and while there was no mention of an injury to the 31-year-old on Saturday, he has also picked up an unexplained problem which will require a once-over.
In Maguire's absence, Everton's Jarrad Branthwaite could now come into contention for his senior England
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