Manchester United "will be in trouble" in April and May if they continue to progress in the Europa League and the FA Cup, says manager Jose Mourinho.
Mourinho is worried about fixture congestion towards the end of the season.
United, who entertain Saint-Etienne in the Europa League on Thursday, are at Championship side Blackburn in the fifth round of the FA Cup on Sunday.
"We cannot choose competitions at Manchester United," said Mourinho.
United are sixth in the Premier League, two points behind fourth-placed Arsenal with 13 matches remaining.
Their next top-flight game is at home to Bournemouth on 4 March, by which time Mourinho could have secured his first major trophy as United boss.