The Champions League holders host the Hammers with a victory vital for their hopes of finishing in the top four and qualifying for Europe's elite competition after being knocked out in the group stages this year.
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"It's a big game, particularly in the first few years I was here [at Chelsea] - less so now as time's gone by but it's a big game and comes at a very important time for us," he told the club's official website.
"Because of the cup games that have been going on we must keep our eye firmly on the league and where we want to finish because of what it means for next season, so for us it's a massive game.
"For West Ham I think they're pretty much secure now in the league but a London derby will always bring an extra edge to it anyway."
The Blues are two points clear of fifth-placed Arsenal and have a game in hand over Arsene Wenger's men, with upcoming tests against Manchester United in an FA Cup quarter-final replay and Russian side Rubin Kazan in the Europa League.