Gianfranco Zola says Watford will “have to play the game of our life” if they are to shock Manchester City at the Etihad Stadium tomorrow but he maintains the opportunity to take on the Premier League champions is “important” in his side’s ongoing quest for improvement.

The Hornets, who will be backed by a 6,000-strong army of fans, go into the FA Cup third round tie priced as big as 18-1 to cause an upset against Roberto Mancini’s side and his former Italian team-mate is set to face some key selection issues ahead of the contest.

A late decision is likely to be made on the fitness of keeper Manuel Almunia after he sustained a hamstring problem in the first half of Tuesday’s 4-3 defeat against Charlton Athletic and played all the second period with strapping on his right thigh.

Almen Abdi sustained a kick to the pelvis in the match and Zola must also decide what strikers to play and whether to make changes to a defence that was poor, individually and collectively, as it shipped four goals.

However, the head coach was hopeful Lloyd Doyley would be available after a month-and-a-half on the sidelines when he spoke to the media on Wednesday, and Nyron Nosworthy is also an option after he was involved in a Watford match-day 18 for the first time in more than three months the previous day.

The City boss also has some selection decisions to make but irrespective of the side he picks, Watford will still be confronted with a team that cost many millions to assemble.

Looking ahead to the trip, Zola, who won the trophy twice as a Chelsea player, said: “It’s not going to be easy but it's OK.

“What I said before, for our team it will be important to play a team like Manchester City. If you want to get better, you need to play against better players so it will be good for us anyway. And in football you never know. It’s quite an unpredictable game.”

Given they are out of the Champions League and currently trail leaders Manchester United by seven points in the top flight, the FA Cup may represent City’s best chance of silverware this season. This could increase the pressure on Mancini’s men tomorrow but the Hornets head coach said: “I’m sure it is a competition they’re taking seriously so therefore we will require a good performance if we want to go through.”

Asked how you go about beating one of the most expensively-assembled teams in history, Zola smiled: “We have to beat them first and then I will tell you.

“Whoever they play, they will be competitive and strong in every single part of the pitch. So we certainly have to play the game of our life and certainly they need to under-perform.”

The Hornets go into the game on the back of a five-match unbeaten run on their travels and are also the Championship’s highest scorers on the road. However, both Tuesday’s defeat and the manner of it were not expected and Zola admitted the following day: “It comes as a surprise to me because we’ve been defending quite well recently and, honestly, I didn’t expect scoring three goals to lose a game anyway. So it’s something we are addressing and we are going to address in the next few days.”

Asked if he considered putting Nosworthy on as a substitute to attempt to firm up the defence, he responded: “I didn’t have the time because we were chasing the game all the time and then we scored the third goal in the second half and how long did it take? 20 seconds to 30 seconds for them to score again, so we were chasing the game and I didn’t have the time to make the changes at the back.”

City will be without eight first-team players for the Hornets’ visit but will still have several internationals to call on.

Sergio Agüero will miss out with a hamstring injury, while Maicon (knee), Jack Rodwell (hamstring), Aleksandar Kolarov (hip) and Micah Richards (knee) are also likely to be absent.

Mancini was dealt a further blow this week, with Yaya and Kolo Toure set to join up with the Ivory Coast squad for the African Cup of Nations tomorrow.

Samir Nasri is suspended after being sent off against Norwich City, while the potential involvement of Mario Balotelli is also in doubt after he was widely pictured having an apparent training ground bust-up with his manager yesterday.