Jonny Evans has insisted Manchester United are not suffering from a lack of confidence.
The Red Devils have endured a surprising dip in form of late, with the club losing two of their last three Premier League matches.
And in the UEFA Champions League on Tuesday night, an unconvincing United display at Old Trafford allowed Porto to net two crucial away goals in a 2-2 quarter-final draw.
Defender Evans, who has emerged as a promising talent this season, has admitted that his team-mates might have been guilty of complacency.
"I don't think there is a confidence issue in this team," he said in the Manchester Evening News. "I just think teams are raising their game against us.
"It's coming to the end of the season and teams need to start winning. Fulham were still trying to avoid relegation and Aston Villa are still trying to reach the Champions League so it was going to be that bit tougher.
"I think it has really been a hectic week, especially with the schedule we've had before that.
"There's no doubt we haven't been defending as well as we have been, but you have stages like that in football. It would be very tough to go the whole season having clean sheets the whole way through.
"Maybe it's been our own fault. Maybe we've become a bit complacent. We haven't been defending for our lives.
"We go into the games really confident. For the first goal I should have done better. It was a mistake, a bad clearance and I should have just stuck it out. But the second goal everyone would be disappointed with it."