Ruben Amorim believes
Manchester United's problem was "clear" after losing a lead against Real Sociedad in the Europa League.
Ruben Amorim pointed the blame at his players' fatigue after United almost collapsed to a defeat against Real Sociedad in their
Europa League last-16 first leg.
The Red Devils looked in control after taking the lead at the Reale Arena before a harsh penalty decision sparked a late onslaught from the hosts.
There was little attacking quality on display in San Sebastian before Joshua Zirkzee stroked Alejandro Garnacho's cutback past Alex Remiro from range just before the hour mark.
United enjoyed a spell of dominance as they searched for a second until VAR adjudged Bruno Fernandes to have handled the ball while defending a set-piece.
Mikel Oyarzabal made no mistake from the spot with 20 minutes to play, during which the visitors had to fight to avoid slipping to defeat.
With the tie perfectly poised for Old Trafford next Thursday, United will have to improve their dire home fortunes since Amorim took charge to progress to the quarter-finals.
During his assessment of the game, the Portuguese tactician put his side's laboured performance after La Real drew level down to fatigue.
"I felt until the penalty, we had the control of the game, and then I think the penalty changed a little bit the momentum," Amorim told TNT Sports.
"I felt our team in the last 30 minutes were really, really tired, and you can feel that in the game. So we take this stage to Old Trafford."
Amorim then warned his players that they would face more pressure to win the second leg because it will be on home turf, where the onus is on them.
He added: "It is going to be a different game. The pressure is going to be on us in that stadium, and we have to be ready.
"I think the key was where we'll be surviving physically until Sunday and ready and fresh until Thursday."