The 34-year-old central midfielder is relishing the prospect of facing his old club at Stamford Bridge on Sunday afternoon, and wants a strong Premier League finish from the Blues
The Champions League holders host the Hammers with a victory vital for their hopes of finishing in the top four next season and qualifying for Europe's elite competition after being knocked out in the group stages this year.
Despite the disappointment of trailing league leaders Manchester United by 22 points, Lampard insists Rafa Benitez's side must forget their Europa League and FA Cup campaigns on Sunday and focus on a strong league finish.
"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, and face Manchester United in an FA Cup quarter-final replay while taking on Russian side Rubin Kazan in the Europa League.