Derby were surprise 1-0 winners in the first leg but United went in at half-time of the return 3-0 up thanks to goals from Nani, John O'Shea and Carlos Tevez.

Derby then threatened an upset when Giles Barnes scored from the penalty spot to put his side back in it.

Cristiano Ronaldo's penalty gave United a two-goal cushion and Giles' second proved to be nothing but a consolation as United claimed their passage to the final with a 4-3 aggregate win.

"If we would have got the second at home maybe things could have been different," Clough told Sky Sports 1.

"We couldn't do anything about the first goal tonight but the second was a killer really.

"Rob Hulse had a good chance with a header but nothing seemed to drop for us. It was good for Giles to get a couple, he's been out for a long time ."

Clough admitted that his side's performance was a marked improvement on his first game in charge which ended in a 2-0 loss against QPR.

"It was a big improvement actually on Saturday," he added.

"We kept playing and plugging away and we showed a lot of character after Saturday. That's what I was looking for."

"United can beat anyone on their day by four, five or six so we have a lot of positives to take from tonight."

Manchester Untied manager Alex Ferguson refused to let his side's injury problems take the shine off his young side's victory.

Youngsters Danny Welbeck, Darron Gibson and Rafael all helped United on their way to a 4-2 win and he chose to sing their praises following the win, rather than concentrate on the injuries picked up by three of his key players tonight.

"We have a few injuries tonight so it has been a bad night in that respect but we are in the final and we should be celebrating that," Ferguson said.

"Finals are always hard to get in to and the young lads have done fantastically well to get there.

"It was a great performance and they (the youngsters) will all be playing in the final.

"The important thing is to find out what their temperament is and they have all proved that tonight.

"Playing in big occasions in front of 75,000 is difficult and I'm proud of them

Jonny Evans, Rafael and Anderson all picked up injuries during the match.

"Anderson's going to have to go for an X-ray," Ferguson added.

"There's some damage. We're not exactly sure what but we'll see what happens

"Evans has had a recurrence of ankle injury that he has been holding for a few weeks, but hopefully he'll be back next week.

"Rafael has a hamstring injury and he'll be out for a few weeks."