Peter Shilton has backed Joe Hart to recover from his poor performance against Wales but says another big error by the England goalkeeper could see the Manchester City man dropped by Roy Hodgson.
Hart was at fault for Wales' goal in England's 2-1 win on Thursday as he allowed Gareth Bale's long-range strike to beat him.
And Shilton, who won a record 125 international caps for his country, says Hart needs to improve his concentration in their final Group B game against Slovakia on Monday.
"I hope it will have no effect," he told Sky Sports News HQ. "Joe's a very experienced goalkeeper and he'd be the first to admit that it was a shot that he should have saved easily.
"Alright, it dipped a little bit, but he didn't get across his goal quick enough.
"I am a member of the goalkeeper's union and I know he also makes terrific saves, but I did think in that game, earlier on he dropped a routine cross and he didn't seem to have his concentration right, but he'll put that right for the next match.
"If Joe makes another bad error then Roy Hodgson would have to look at (dropping him). No player is assured of their place, but Joe is one of those you'd probably put first on the team sheet."
Shilton believes England can go deep in the tournament, but only if Hodgson can figure out his best team as he feels there has been some muddled thinking with regards to selection in the first two games.
"We need to improve," he said. "We dominated both games but I don't think Roy Hodgson picked the right team in the first match and in the first half against Wales.
"It was a forced substitution with Vardy and Sturridge coming on and it paid dividends, but he's got to get a team that know what they're doing, where they are going to get goals from.
"We're a little bit off-the-cuff at the moment and we're going to meet better competition as the tournament goes on. I'm hoping we'll at least get to the quarter-finals and the semis would be a good effort. If we improve, who knows? The tournament is quite an open one."