The French star entered the fray for the final 15 minutes and was on the spot to side-foot home the injury time clincher in our 3-1 victory.
Darren Anderton and Helder Postiga bagged the other goals as we found our form in the fourth round tie. We now play Middlesbrough at home in the quarter-finals.
"I couldn't have come back in a better situation," said Fredi, who has now scored seven goals in his last seven games.
"I have to thank the team because they played a brilliant, brilliant game and I came on at the end and just had to finish it off.
"Fifteen minutes was a good time for me, I've been struggling a little in the last week but it's improving again and I think I need a couple more weeks to be completely fit.
"It's a great feeling to be back. I'm just happy to score. To come on at the end like that is ideal for me at the moment.
"But I give full credit to the team. The first 20 minutes were excellent and we played some amazing football. We were the better side all over the pitch."
Fredi Kanoute described last night's Carling Cup triumph over Manchester City as the perfect return after six weeks out.