Rooney put his turbulent week behind him by firing the only goal at Stamford Bridge to give United the advantage ahead of Tuesday's quarter-final second leg at Old Trafford.
Chelsea 0 Man United 1: Rooney the hero for Fergie as United claim advantage Roo's happy now: Wayne Rooney celebrates his goal for United at Stamford Bridge on Wednesday night
United can count themselves lucky after referee Alberto Mallenco failed to award Chelsea a blatant penalty when Patrice Evra tripped Ramires in the closing stages. Not that United manager Sir Alex Ferguson showed any concern over his side's good fortune.
Ferguson said: 'Someone said it could have been a penalty. It's the first penalty decision we've had in seven years, so we're due one.
'But I don't feel guilty about thatat all. It looked as if the boy (Ramires) made the most of it. It was a50-50 (challenge) from where I was and I don't know what the contactsituation was.'
On underfire Rooney's display, Ferguson added: 'He took a great lot of abuse and late tackles on him, but he was excellent.
In the corner: Rooney scores the only goal of the game after sliding the ball in off the post
'His work-rate, desire - he was top quality. He's now been more regular with his goalscoring which, in the last part of the season, is going to be important to us.'
Fergie now believes that the 'electric atmosphere' at Old Trafford next Tuesday can propel his side into the Champions League semi-final.
Ferguson said of the victory: 'It's an advantage, but the biggest advantage is Old Trafford. It'll be an electric atmosphere. We have to be very careful and have to play a top performance, but the atmosphere will help us. It'll be a tight game at Old Trafford. I hope we get through Saturday's game without any further injuries.'
Concerns: United defender Rafael will have scans on a knee injury on Thursday
United play Fulham on Saturday when midfielder Anderson, who plays in the reserves tonight, is set to return from injury.
Ferguson's only concern at Stamford Bridge was seeing fullback Rafael being carried off with a knee injury, which forced Antonio Valencia to be pressed into service as a makeshift right-back.
In contrast Rio Ferdinand returned after two months sidelined by injury and, alongside Nemanja Vidic, gave United's defence solidity.
Ferguson said: 'We've had to make do with defenders most of the season, but we've somehow managed to get through that. With Ferdinand back, there's evidence things will get better. The experience of Rio is fantastic. It was really important to get him back. The squad's getting stronger.'
Heads, you win: The United striker goes head over heels after scoring the only goal of the game
And when asked about the possibility ofdoing the treble to emulate his 1999 team, he said: 'I've never thoughtabout the treble. I said we're in every competition and we'll try ourbest. When you go out on that field, you have to win the game. That'sthe attitude of Manchester United. We have to do that.'
Chelsea's ?50million striker Fernando Torres was booked for diving in the area late in the game under the challenge of Antonio Valencia - a decision Ferguson fully agreed with.
But Chelsea manager Carlo Ancelotti stormed on to the pitch after the final whistle to confront Mallenco about his decision to refuse the home side a late spot kick after the Ramires incident, and the Italian accused the Spanish official of bottling it, saying: 'It was clear, for everyone.
Top dog: Ferdinand celebrates Rooney's goal with team-mates
'Everyone knows it was a clearpenalty. The problem is I know it's sometimes not easy to give thepenalty in the last minute, and you need to have personality, courageand character. Not always do referees have these kind of skills.
'I'm disappointed but this is the result. This is the past. Not just the referee, but the assistant was in the right position to decide that was a penalty.
'Obviously we know it will be difficult to win at Old Trafford, but we have confidence to do it. We had to win at Old Trafford last year to win the league and we did.'
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Explore more:People: Alex Ferguson, Wayne Rooney, Patrice Evra, Fernando Torres, Antonio Valencia, Carlo Ancelotti, Nemanja Vidic, Rio Ferdinand Places: Manchester