Danny Welbeck is a doubt for England's World Cup opener against Italy after limping out of training on Tuesday, according to a number of British newspapers.
He was seen leaving the session with his thigh strapped after receiving treatment from physio Gary Lewin.
Welbeck was widely expected to start against Italy on Saturday after beginning two of England's three warm-up fixtures, the 3-0 win over Peru and the 0-0 draw with Honduras, and playing on the left wing in both matches.
The 23-year-old, who has won 24 caps, has been a regular during Roy Hodgson's two-year spell in charge and all eight of his international goals have come during his fellow Englishman's reign.
If Welbeck is ruled out of the Italy game, it could allow Liverpool's Raheem Sterling, who has only played 39 minutes in the three friendlies and was sent off in the 2-2 draw against Ecuador, to start in Manaus.
Hodgson said that Sterling, who was suspended for the Honduras game, is "fit as a flea" and insisted he would have no qualms about picking the teenager.
He told national newspapers: "If you're asking me will I hide behind that, to not consider him, then no I won't because he's as fit as a flea and I'm pretty certain he hasn't forgotten how to play matches, either.
"It was unfortunate that he couldn't play against Honduras but I can tell you that Raheem Sterling is very much in the group of players I'm considering.
"If I select him, it won't be in my opinion a risk that he hasn't played so many minutes. And if I don't select him, it certainly won't be because he has only played 39 minutes. It will be because I prefer someone else. That's all I can tell you."
England will definitely be without Arsenal midfielder Alex Oxlade-Chamberlain, who Hodgson expects to recover from his knee injury in time for their second Group D game, against Uruguay on June 19.