Tony Mowbray insists
Rooney's goal opened the floodgates for United before quick-fire goals from Cristiano Ronaldo, Dimitar Berbatov and Nani compounded
"I said after we beat Fulham you could feel the quality of the Premier League - and it's on a different level to that at United," the
"Ninety per cent of Premier League teams have quality in the front areas of the pitch.
"That is very evident at United.
"Despite it being 0-0 for 50-odd minutes, that quality is always likely to hurt you.
"Ultimately, it did this evening.
"I was a bit disappointed we defended so naively in the last 20 minutes.
"But generally I have good, positive thoughts."
The defeat leaves Albion in 10th place in the Barclay's Premier League with Mowbray insisting spirits are still high as the Baggies now prepare to face Hull City at The Hawthorns on Saturday (KO 3PM).
"Spirits are fine," Mowbray continued.
"We're not being judged on that game.
"Supporters have come here and are disappointed we lost 4-0.
"We're all disappointed.
"But I thought for long periods we showed we can compete in areas of the pitch.
"Their quality at the top end of the pitch won them the game.
"That's football and there is no shame in it.
"I thought we did fine."
Mowbray added: "I don't know how other teams approach it at Old Trafford but I thought we were as positive as we could be.
"You can play 4-3-3 or 4-4-2, but who marks Berbatov when he drops into the hole between your midfield and defence?
"Who picks up Rooney when he drops in there and turns?
"You've got to have a game-plan to prevent it and for 55 minutes I thought we did it pretty well.
"I don't think they had too many efforts at our goal before that.
"There was one Rooney header from a corner but I don't remember a lot else, really.
"They had plenty of the ball in front of us but we had the ball for spells.
"Then, all of sudden, they scored.
"It loosened the shackles a bit and we had to be a bit more adventurous.
"Then it was two, three and four and it was finished."