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.
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.
His side face Southampton in the EFL Cup final at Wembley on 26 February, which means the league derby at Manchester City scheduled for the same day has been postponed.
“We know our situation is really complicated,” added Mourinho.
“The Europa League is a competition where we play on Thursdays and that makes it even more difficult for us.
“With the accumulation of FA Cup, League Cup and match postponed it is really hard for us.
“If you progress in the competitions, we will be in trouble in April and May. But we cannot choose competitions so we play to win.”
United have played 38 competitive games this season, including 25 in the Premier League, five in the EFL Cup and two in the FA Cup.
Thursday’s Europa League last-32 first leg tie at Old Trafford will be their seventh in this season’s competition. That cup provides United with one of two possible routes into next season’s Champions League.
The winners of the final on 24 May will get a Champions League spot, while United will also qualify if they secure a top-four finish in the Premier League.
United are sixth in the Premier League, two points behind fourth-placed Arsenal with 13 matches remaining.
Mourinho added: “We have two doors still open. But we are in the last 32 – not eight or four so there is a long way to go.
“There is also a long way to go in the Premier League.”