But this time it wasn't the match officials that were the target of Fergie's ire, instead the gaffer rapped his players for not backing Ronaldo over the 90 minutes.

Despite missing a third-minute penalty, Ronaldo was United's most dangerous player as they drew 0-0 at the Nou Camp.

Ferguson said: "In Cristiano Ronaldo, I thought we had a player who could win the match. He was a constant threat and I thought that, with better support, we could have won."

Ferguson felt let down by his side's midfield, saying: "I am bit disappointed in the transition between defence and attack.

"We are normally better at keeping possession of the ball, that causes more concern than any other part of the game."

The United boss also claimed his side gave away possession too often.

He said: "We will analyse (why we didn't score) in the next two to three days, but we lacked penetration. We were not quick enough out of central areas and when you give the ball away at this level, you have to go back and defend."

Wayne Rooney and Park Ji-Sung were asked to play in unfamiliar roles and Ferguson believes those changes affected his side.

"Asking Rooney to play a different position and Park as well obliged us to defend more," he said.

United were also rocked by the absence of centre-back Nemanja Vidic, who missed the game with a stomach problem.

But Ferguson believes the Premier League leaders coped well without the Serbia defender.

"Without Vidic, it meant the reshuffle," he explained.

"I decided to go with Wes Brown because of experience. It would have been a bit unfair to place the responsibility on Gerard Pique against his old club. (Rio) Ferdinand played well and looked strong throughout the game."