CITY will find out tonight who stands in their way of reaching the last eight of the FA Cup for the first time in 39 years.

Fulham and Sunderland go at it for a second time at Craven Cottage after their goalless encounter on Wearside ten days ago.

The winners book a fifth-round trip to Valley Parade a week on Sunday to try and do what Chelsea failed to and topple the giant-killing Bantams.

Whoever emerges victorious from the replay, one thing is guaranteed. They will have to reword their team talk for the City clash.

Of the many remarkable features of City's performance at Stamford Bridge, the one area that stood out above all others was the level of fitness.

Phil Parkinson's team pride themselves on going to the very end – but to do it against the best team in the country was something that nobody could have envisaged.

But the proof was there. Three of City's goals were scored in the final 15 minutes – and all after Jose Mourinho had beefed up his ranks with a few of the big-hitters.

Willian and Cesc Fabregas came on with Chelsea 2-1 up, and Eden Hazard when the scores were level, but City showed no sign of wavering in the face of that additional talent.

Nick Allamby, the club's head of sports science, said: "Fitness is something we do pride ourselves on. We are big on the sports science and physical preparation side and every little thing we can do to make sure the players are right.

"But I was so pleased at how we managed to keep going at Chelsea. We had a game plan how the manager wanted us to play and it was about whether we could sustain it.

"Often when you're playing higher-division clubs, you know there will be a fair few managers who will say in the team talk that 'the lower team will tire'.

"The longer the game goes on, the more they will have the advantage with fitness. Clubs in higher leagues always think that will be the case.

"They've lots of facilities, lots of money, lots of staff – every advantage over clubs from the lower divisions.

"When you are down at our level, the endurance side becomes so important because of the number of league games we play.

"It's a different type of game to the Premier League, with a lot more running and covering ground. But they are more powerful and do a lot more sprints.

"Like any sport, the best players tend to be the best players physically. They end up being quicker and more powerful.

"But we try to cover every aspect of fitness, power, speed, change of direction. We try to cover it all."

The role of Allamby in City's progress under Parkinson has been highlighted before but was never more evident than during a fightback that will be talked about for years.

Allamby can pinpoint the exact moment when he knew City had a chance – when Jose Mourinho rose from the Chelsea dugout.

The City fitness guru reflected: "He always sits down really cool as if nothing is bothering him. Then ten minutes into the second half he stood up and went into the technical area.

"At that point, I remember turning to somebody on the bench and saying 'we've got them rattled'.

"We came out so strong and determined for the second half and built up momentum. You could feel we were going to get the equaliser.

"Watching the second half again, it was the best performance I have ever been involved in – especially considering who we were playing.

"There was so much adrenaline kicking in, I hadn't realised until I watched Match of the Day that it was 2-1 when Willian and Fabregas came on and 2-2 when they brought on Hazard.

"To then score three goals in the last 15 minutes like that was something we were very proud of.

"The league has always been the priority but we never expected a performance and a result like that."

You can be sure that Fulham and Sunderland will be preparing for that now.