David Moyes conceded his Manchester United side lacked intensity after they suffered their third defeat of the Premier League season at home, 2-1 to West Brom.
United fell behind to a magical goal from Morgan Amalfitano, who slalomed past two players prior to finishing, before Wayne Rooney drew them level with a free kick from the left flank.
But a fine strike from Saido Berahino restored West Brom's lead and they saw out the remaining time to record their first win at Old Trafford since 1978.
It means United have lost three of their opening six league games for the first time since the 1989-90 season and they sit 13th in the Premier League table.
A dejected Moyes told MUTV: "It was a poor result and a poor performance - we never really got going. We lacked an intensity and spark to our game, and in the end they deserved the win, I can’t argue with that.
"In the first half we had a lot of the ball and tried to move it - we probably controlled a lot of the game - but I thought for all our possession we didn't create a lot of opportunities. And when we did, we didn't take them.
"They had a couple of chances on the break and the more we went for it, the more chances they seemed to get.
"We had plenty of forward players out there but we're just not opening teams up. I'm concerned after today but there are a lot of games to go and we'll try to put it right."
After starting with Japan international Shinji Kagawa on the left, Moyes replaced him with 18-year-old Adnan Januzaj at half time.
"We want Shinji to feel he's getting an opportunity to show what he can do and his best position may be number 10," Moyes said.
"But even for Japan he plays off the left as well so it's not something which is strange to him or a position he's not used to. There's a lot of competition here and we want to push each other."