Manchester United manager Alex Ferguson admitted his side's crippling injury crisis played a major part in their exit.
The Premiership champions were without Ryan Giggs, who failed a late fitness test on his hamstring injury, goalkeeper and captain Peter Schmeichel and Gary Pallister.
Ferguson said: "It was a blow to us, there's no doubt about that. If we'd had some more regular, consistent team selections I think we'd have beaten them. I don't think they were on top, they only had one shot on goal and that was the goal, but it was a good start for them and it meant they were quite comfortable on the ball. They got an away goal after five minutes and it was a killer."
Despite seeing his European hopes shattered once again, Ferguson admitted he had no complaints about his side's commitment.
"I don't know what you can say to them because they had a lot of enthusiasm, some of the football was good at times and I think we were a but unlucky on the night," he said. "I'm quite satisfied with the players, they've given everything they possibly could, and that's what the fans expected and what I expected."
He also believed his team were robbed of a clear-cut penalty when Martin Djetou handled Teddy Sheringham's overhead kick in the first half and added: "We had one or two chances just before half-time and we should have had a penalty kick, it was a clear handball. In these situations you need a break like that. But personally, I don't understand the referees in Europe."
Scotland and Monaco star John Collins admitted United's injury blows had given his side a boost and said: "They put us under a bit of pressure but we scored and it's important to get away goals in Europe.
"The fact that they were without Ryan Giggs, who has been in fine form this season, and Peter Schmeichel, who has a great influence on their back line, was a massive boost for us.
"We're in the last four so it's possible that we could win and we'll give it our best shot."