The Hammers will host the Premier League champions at Upton Park following City's disappointing 2-2 draw with CSKA Moscow on Tuesday, which has dampened their hopes of reaching the knockout rounds of the Champions League.
"We've got a different team to when we played Man City last season," Allardyce said in this morning's press conference.
"They're a fabulous side but if we're going to challenge them at any time this season this might be it, coming off a Champions League game. If we can keep their superb attacking force quiet we'll then have to see if we can exploit any weaknesses."
West Ham, who currently occupy the final Champions League spot in the table, are four points behind second-placed City after eight games.