Kevin De Bruyne could not comprehend how Manchester City lost to Manchester United in the second leg of their EFL Cup semi-final.
City went down 1-0 at Etihad Stadium on Wednesday, but the holders still progressed with a 3-2 aggregate victory to set up a final against Aston Villa.
Pep Guardiola's side - who are in the hunt for a third straight EFL Cup title - wasted a glut of glaring chances, with Raheem Sterling missing two notable opportunities while David De Gea was also in good form for United.
But with goalscorer Nemanja Matic sent off, United failed to make City pay for their profligacy, and De Bruyne knows his side must take heed from their mistakes.
"I think so," De Bruyne told Sky Sports when asked if it was a relief to hear the final whistle.
"I can't even comprehend how we lost this game. For me, United didn't even have one chance. We were way too wasteful. We have to learn from this but at least it's good we got into the final.
"I think we got sloppy. The goal, we didn't clear the lines well and they scored. After, I don't think United had one more chance but they only needed one to score.
"In the end, we fought for what we had and we need to learn from the mistakes."
However, De Bruyne dismissed the suggestion City's defeat would tarnish their progression to a third consecutive final in the competition.
"Of course not. If we win the final, nobody will talk about this game," he added. "It's not nice and we should have done better but it's just the way it goes sometimes.
"It's beautiful. I've been lucky in the five years I've been here to go [to Wembley] seven or eight times now.
"It means we're doing really well. It's always a nice day and now we're going to fight to win the cup."
Meanwhile, Ilkay Gundogan echoed De Bruyne's sentiments, but he believes City displayed the resilience they will need when they meet Real Madrid in the last 16 of the Champions League.
"I totally agree, we should have scored early in the first half. We started well but, after United scored, we were a bit sloppy," he said.
"We should have scored at least one or two goals today but it was not meant to be.
"It was a great test for the Real Madrid games. The manager said before the game it was an experience we had to survive and to overcome.
"I think we can improve - it's a learning process. We will analyse and try to make it better."