Speaking to BBC Sport, post-match, Knockaert said Albion came out 'with a lot of credit' despite a 1-0 defeat.
He said: "I think we gave everything. We had a game plan and it was really tough. We conceded in the first few minutes and I think the Man City fans and the people watching on TV thought it would have been four or five at the end.
"What the lads put in today was incredible. We come out of this cup with a lot of credit. We played against the champions and they may be champions again this year. I can't remember a clear chance for them apart from the goal."
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Knockaert said he has been left with 'two feelings'.
He added: "I am really disappointed because I felt we could have got something. At the same time I am really happy because if we talk about budget, a team with amazing players, what we showed today was incredible.
"If I am honest it is one of the best games I have played in my life for a few reasons. When you have a chance to play a kind of game like this you enjoy it. When we came out of the hotel we saw our fans behind us and it gives us a massive push. What what we did today I think they will be really proud of us."