Sir Alex Ferguson offered no excuses after his Manchester United side were upset by Norwich at Carrow Road.
Anthony Pilkington's second-half header condemned United - missing the ill Wayne Rooney - to a first league defeat since September.
Ferguson said: "We're disappointed to lose the game but we have to give credit to Norwich for the way they fought and battled for every ball on the pitch.
"They defended fantastically well and the goalkeeper also had a really good night so it's disappointing.
"It was a marvellous cross and a marvellous touch for their goal so our goalkeeper could do nothing about that. They deserved the win just because they worked so hard for it.
"The players are used to making comebacks and we're always a threat in the last minutes of matches. We had a lot of half-chances but it just wasn't our night."
Rooney was out with tonsilitis, and Ferguson said: "We always miss our good players but we had plenty of good players on the pitch."
Adebayo Akinfenwa bagged a goal in each half, the second coming from the penalty spot, to move to 12 for the season .
Chris Hackett added a third goal before Joel Grant reduced the arrears from the penalty spot for a Wycombe team that held their own for long periods but slipped to the bottom of the table.
Boothroyd said: "I was pleased with our first half performance, we dominated the game and deserved to be a couple of goals up, but not our second half display. We made some daft decisions on the ball in the second half and we looked mentally tired at the end.
"Obviously, I'm pleased we've got the three points but I've told the players that the second half performance wasn't good enough. On another day that would have ended up a draw if we hadn't been so clinical in front of goal.
"We've had some long trips recently but I can't use that as an excuse, it's the same for all clubs in this league. At least we dug in, weathered the storm and got the result.
