Manchester United boss Louis van Gaal says fans were right to boo him at the end of the game against Southampton.
The Red Devils suffered their sixth defeat of the season in the Premier League after Charlie Austin scored in the dying minute of the game.
They dropped out of the Top Four after Tottenham Hotspur registered an important 3-1 win away at Crystal Palace.
"I had a feeling they could score only from a set-play," van Gaal told BBC Sport.
"Our defence in set-plays was weaker because I changed Fellaini and had to change Darmian. Every change was a weakness in defence.
"I wanted to win this game and that's why I changed Cameron Borthwick-Jackson for Adnan Januzaj. That is a risk you take, it was a poor game and we didn't create so much and neither did our opponent.
"Because you have to meet expectation and expectations are very high, that gives a lot of pressure for the players.
"They [the supporters] are right, I cannot deny that. I have seen the match also. In better or for worse we have to stick together.
"We are working very hard but we have a lot of injuries that you cannot change."