Black Stars deputy skipper had a hand in Lanzini's goal that dashed Tottenham title hopes on Friday night.
Andre Ayew was impressive throughout the game and ,his long ball should have been connected home by Lanzini, yet he missed the goal post by some few inches in the early minutes.
Spurs could have narrowed the gap to a point with victory at London Stadium, but were well below par as the Hammers helped Chelsea close on the title.
Hammers keeper Adrian made first-half saves from Harry Kane and Eric Dier before Lanzini smashed in a loose ball.
Chelsea need two wins from their final four games to be crowned champions.
Tottenham must hope the Blues slip up in a favourable-looking run-in, which includes home games against three sides in the bottom seven.
Antonio Conte's side will secure the title on Friday, 12 May if they beat both Middlesbrough and West Brom.
The Spurs players looked disconsolate as they trudged off the pitch, their heads bowed, while their West Ham counterparts - and the home fans - took great delight in harming their neighbours' title ambitions.