Manchester United's players will endure a huge mental test in the Europa League, says Tottenham head coach Mauricio Pochettino.
Louis van Gaal's team weredumped out of the Champions League on Tuesday night with defeat at Wolfsburgwhich meant they finished third in their group and instead progressed to the second tier European competition.
It is a challenge Spurs have got used to. They will top their Europa League group if they get a point against Monaco on Thursday and they are fifth in the Premier League having dealt with tricky away trips and a Thursday-Sunday playing schedule.
Pochettino said: "It's a big, big difference. When you play Thursday and Sunday, it can affect the mentality and the psychology of the players.
"Thursday night, [long] travel and you need to play Sunday afternoon. Always for the player it affects them. Football is [supposed to be] Saturday three o'clock.
"It's never easy. You never know how it will affect you. But it's true that, for now, United must feel very disappointed because they had the possibility to go through to the next round.
"It's true that's a different competition and you have to change your approach. It's tough for them, but you never know. It's about how you develop your game."
United midfielder Marouane Fellaini admitted on Wednesday the team's new European assignment threatened their assault on the Premier League by saying: "When you play Thursday it is closer to the weekend, so it will be tough."
The Old Trafford club are fourth, three points ahead of Spurs, and Pochettino warned English clubs will continue to struggle in Europe because the top flight is so hard.
The Argentine added: "In Spain, for example, the clubs use the local competition to give players rest and recovery from the Champions League.
"'For us it's impossible. The Premier League is the toughest competition, this is the reality. Last weekend, Liverpool went to Newcastle and lost, Chelsea played Bournemouth and lost, Manchester City lost in Stoke - in Spain that wouldn't happen."