Manchester United captain Harry Maguire says a slow start against RB Leipzig cost them a place in the last 16 of the Champions League.
United only needed a draw in Germany on Tuesday night to secure a place in the knockout stages and Ole Gunnar Solskjaer's side had already beaten Leipzig 5-0 earlier in the campaign.
However, United were 2-0 down after 15 minutes and never recovered from a poor start even though they came close in the send.
Maguire told BT Sport: "We started the game too slow, wasn't good enough the first 20 minutes we weren't at it.
"They scored the two chances they get, they put two balls in the box and we fail to deal with the cross.
"That's why we've been beaten because the second half we gave everything and they've scored their only attack, another cross.
"We have to look at ourselves, we gave ourselves too much to do. We've been coming from behind so we had great belief we could do it
"You've seen how close we came at the end, the amount of chances we've had, the shots we've had but we started too slow and we can't keep falling behind."
"We said in the game on Saturday at half-time, 2-0 down, the next goal is crucial and we said it again tonight.
"We piled all sorts of pressure on them and then they go and score in their first attack
"They make it 3-0 and the task becomes even bigger. We still had belief but the third goal proved to be the crucial one in the end.
"Even when we did three down we had belief that we needed to score the next goal, we managed to do it and you saw how close we came at the end but we didn't start the game well enough."
Solskjaer opted for a defensive three and wing backs, something he's done on several occasions in the past to give them more solidity in defence.
Maguire said a change in formation couldn't be used as an excuse for the defeat.
"I don't want to look at excuses. As a player out there, there's 11 bodies out there, we have to go out and be aggressive, win the first balls, win the second balls, defend crosses, it's the basics of football.
"It doesn't matter what shape your in, if you can't defend crosses you're going to lose football matches.
"I don't want to look at shape - it's not an excuse".
United had the toughest group of the four Premier League clubs in the Champions League but wins over PSG and Leipzig in their opening two games put the Red Devils in pole position to qualify.
"It's a tough group but we looked at the group and we felt we should get through," Maguire said about the group.
"That's the standards of this club. I'm the captain, I'm gutted for everyone, we worked so hard last season to reach this competition.
"No matter what group we got it was going to be tough because you're playing against good teams but we have to do more."
United are back in Premier League action on Saturday when Manchester City visit Old Trafford for the derby.