Derby County boss Nigel Clough said his side had a great opportunity to take a massive scalp in Manchester United but missed the boat.
After taking a1-0 lead into the second leg, the Rams couldn't hold out the reigning Premier League champs eventually going down 4-3 on aggregate.
"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.
"It was a big improvement actually on Saturday," he said of the 2-0 Championship loss to QPR.
"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."