Sam Allardyce brands Manchester City a bit Jekyll and Hyde this season

Sam Allardyce. Photo: PA

West Ham will take confidence going in to their clash with Manchester City from both their memorable win at Tottenham and City's own faltering away form.

Sam Allardyce led the Hammers to a 3-0 victory at White Hart Lane before the international break after deploying a formation without a recognised striker.

City are the visitors to Upton Park on Saturday evening as West Ham look to build on their London derby success and Allardyce feels there is cause for optimism given the away form of Manuel Pellegrini's side.

"In terms of results they've been a little bit Jekyll and Hyde," Allardyce said.

"[They are] absolutely fantastic at home and unfortunately for them they've not won away from home yet - lost two and drawn one.

"We have to be encouraged by that. Last year we had a fantastic 0-0 against them."

City have lost at Cardiff and Aston Villa on their Barclays Premier League travels so far this season, with their only point on the road coming in a 0-0 draw at Stoke.

West Ham had won only once in the league until their success at Tottenham and Allardyce knows his squad need to put in another top-drawer performance if they are to take three points in front of their own fans for the first time since the opening day.

"Our top level players have to play at their top level as they did against Tottenham," he added.

"Anything less would make life difficult with the quality of their squad. If our players can exploit their weaknesses like we did against Tottenham I don't think we'll win 3-0 but I hope we do."

Allardyce revealed the decision not to play a striker at Spurs stemmed from the fact none of his fit forwards had found the back of the net with great regularity.

With Andy Carroll sidelined and Carlton Cole still searching for match fitness after signing a short-term deal, Allardyce still only has Mladen Petric, Ricardo Vaz Te and Modibo Maiga to choose from.

But Allardyce's main worry ahead of this weekend comes in defence where he will now be without James Collins, who suffered a hamstring injury whilst on international duty with Wales.

Although the 30-year-old has not featured in the previous two Premier League games, Allardyce believes his squad will be stretched to the limit with Winston Reid and James Tomkins his only fit centre-backs.

"I am concerned about the fact that we only run with three centre-halves," Allardyce said.

"So James being out is a particular problem for me because I have to run with only two central defenders now, James Tomkins and Winston Reid, for however long it takes James to get fit again, that is my big concern.

"He [Collins] has been excellent and he has been very unfortunate that I decided to leave him out.

"It wasn't that he was playing badly it is just that I thought James [Tomkins] in the Cardiff game in the Capital One Cup gave a fantastic performance and that fantastic performance got him in the team."