Mark Hughes watched his weary City players fall over the line into the last 16 of the Carling Cup and admitted: "At the end, a few of our guys were out on their feet."
Blues' performance against a surprisingly solid Fulham side was a case of "after the Lord Mayor's Show" following the spectacular but demanding 4-3 derby defeat at Old Trafford on Sunday.
Zoltan Gera gave bogey team Fulham the lead and a near full-strength City side were taken to extra time before skipper Kolo Toure's header from a corner killed the threat of penalties.
Manager Hughes admitted: "It was a difficult night. Fulham scoring first was exactly what they wanted. They were very well organised, with plenty of players behind the ball and difficult to break down.
"We had to be patient, keep the ball moving and create things, because with Craig, Carlos and Shaun up front knocking high balls into their penalty box isn't an option. But we stuck at it and we are in the next round, which was the object.
"There was a lot of physical and emotional effort at the weekend. At times we looked drained because of that, and we were up against a team with a lot of energy fielding players who didn't play at the weekend.
"In the early part of last season we didn't look a threat at set pieces, now we always look as if we can score at set plays. We try to get them to be a bit more dynamic in the box. If you get first contact, invariably something happens.
"But we needed to step it up in the second half and ask a few more questions. We had to be a bit more forceful in breaking their lines."
Fulham boss Roy Hodgson, who picked a completely different team from the weekend, said: "It was a marvellous performance. I thought we'd be hard to beat and stretch City, but they took it to a better level."