Manchester United manager Jose Mourinho said his players were "masters in complication" after their defeat by bottom side West Brom at Old Trafford.
The result saw Manchester City crowned Premier League champions, as they lead second-placed United by 16 points with five games each to play.
Albion secured the win thanks to a Jay Rodriguez header from Chris Brunt's corner as the home side failed to clear their lines.
"It was a bad reaction after the City victory, the consequence of that is complicated football," Mourinho said.
"Some players think it is stylish football. We were a complicated team and let them feel comfortable."
United's best chance of the game was a Romelu Lukaku header, which was superbly saved by Albion goalkeeper Ben Foster.
City manager Pep Guardiola had claimed he would be on the golf course on Sunday afternoon and would not watch the game.
The win was West Brom's first since a 2-0 success over Brighton on 12 January and only their fourth all season.
However, Premier League survival still looks unlikely for the Baggies, who are nine points adrift of 17th-placed Swansea with four matches remaining.