East meets west in a game which neither club can afford to lose at Stamford Bridge on Saturday.
Chelsea can take advantage of Manchester United not being in action until Sunday by reclaiming top spot, while time is running out for the Hammers to give themselves breathing room at the wrong end of the table.
The Blues have had two weeks to lick their wounds following a 4-2 humiliation for John Terry and company at the hands of Manchester City on February 27.
They were effective in sending Stoke City packing from the FA Cup at the sixth-round stage last weekend, but Chelsea have been far from their clinical best since losing to Everton in the league at the beginning of last month.
Injuries are certainly not helping coach Carlo Ancelotti, who will once again be without the likes of Petr Cech (calf), Ashley Cole (ankle), Michael Essien, Jose Bosingwa and Deco (all knee).
Michael Ballack and Juliano Belletti are both available after missing the Stoke game through suspension.
Meanwhile, West Ham's mini-revival following the takeover of the club by David Gold and David Sullivan in January is in danger of petering out.