David de Gea will have a scan on his injured knee on Friday, according to Sky sources.
De Gea suffered the injury as he warmed up before Manchester United's Europa defeat to FC Midtjylland on Thursday.
The Spain goalkeeper appeared to land awkwardly as he made a routine save in the on-field pre-match preparations and was forced to retire to the away dressing room for treatment.
Despite efforts from the United physio team, De Gea failed to recover in time for the start of the match and was replaced by Sergio Romero in Louis van Gaal's starting line-up.
The United squad returned to Manchester straight after the game and De Gea will be assessed at their Carrington training base.
Van Gaal said after the 2-1 loss: "It happened in the warm-up and we didn't know that, so we will have to wait and see the scan tomorrow.
"Then maybe we can say more but it was a big surprise."
United were unable to name a goalkeeper among their substitutes after taking just De Gea and Romero across the North Sea.
United recently loaned goalkeepers, Victor Valdes and Sam Johnstone, to Standard Liege and Preston respectively.
The latter is likely to be recalled in order to provide cover for Romero, if De Gea fails to recover in time for Monday's game.