Ole Gunnar Solskjaer admitted David de Gea made an inexplicable error as Manchester United slumped to a 3-1 defeat against Chelsea in the FA Cup semi-final at Wembley.
The Spanish goalkeeper has been frequently lauded as one of the world's best by his United manager, but significant errors have crept into his game and Sunday's cup clash was one he will want to forget.
As well as being beaten by a close-range Olivier Giroud shot that he might have kept out on another day, De Gea let a skidding shot from Mason Mount slip under his body to allow Chelsea a 2-0 lead.
Solskjaer acknowledged De Gea should have done better, telling the BBC: "He knows he should save that one 100 times out of 100 but that's football for you. I made the decision to play him and mentally he was ready for it."
In a subsequent media conference, Solskjaer was asked whether he might have a choice to make about his goalkeeper position in future, given the number of times De Gea has been at fault.
He made it clear De Gea, like every United player, must justify his place in the team.
"Obviously, everyone has to perform and everyone has a chance every time we perform to stake a claim in the team," Solskjaer said.
"David knows he should have saved the second goal but that's done now, we've got to move on.
"It's hard for a keeper to make amends, apart from David making two or three fantastic saves after."
In his television interview, Solskjaer said United, having seen one chance of silverware disappear, needed to take the right attitude into their final two Premier League games against West Ham and Leicester City and the subsequent battle for a European trophy.
"There is no time to feel sorry for ourselves," Solskjaer told BBC Sport. "We have two games this week and then the Europa League. We will get our heads ready and our legs ready and go again."