Ole Gunnar Solskjaer has refused to disclose further information about why David de Gea was missing from Manchester United's 0-0 draw against Crystal Palace on Wednesday.
But he has hinted that the Spanish goalkeeper could be absent for some time as he deals with a 'private matter'.
There has been a fierce battle between De Gea and Dean Henderson for the No.1 jersey this season, with the former tending to get the nod for Premier League games and the latter featuring in the cups.
But there was no sign of De Gea against the Eagles, with Henderson starting between the sticks and third choice Lee Grant on the bench.
© PADean Henderson kept another clean sheet in Manchester United's 0-0 draw with Crystal Palace
Ahead of the game Solskjaer simply said the 30-year-old was left out for "personal reasons".
And he repeated the same line to MUTV afterwards, and would not be drawn on when De Gea may return.
His absence does potentially open the door for Henderson to string together a successive run of games and gives him the opportunity to impress Solskjaer.
The England shot-stopper has kept a clean sheet in his last four appearances in a row, and is putting a great deal of pressure on De Gea's place.
And Solskjaer appeared happy with Henderson's display against Palace after he saved his side with an important stop from Patrick van Aanholt's efforts right at the death.
"That's a Man Utd goalkeeper, sometimes you have to keep concentrating," Solskjaer said. "He's growing in that position. I thank him for one point and not zero."
© Pool via REUTERSIt is not clear exactly how long David de Gea will be out for
It is looking likely Henderson will start the Manchester derby at the weekend, in which he will no doubt be a great deal busier than he was during Wednesday's dreadful game.
There has been speculation recently that Henderson could attempt to force a move away from Old Trafford in the summer unless he is given more minutes in the Premier League.
But this could well prove to be the chance he has been waiting for, and it remains to be seen how long he ends up keeping his position for.