Chelsea scored a goal in each half to see off top-four rivals Everton and maintain Thomas Tuchel's unbeaten start as Blues boss.
The hosts took the lead when Kai Havertz's shot took a big deflection off Toffees defender Ben Godfrey.
England goalkeeper Jordan Pickford made a fine save to deny Chelsea's Marcos Alonso and Havertz thought he had scored, but had handled the ball before finishing.
However, the hosts doubled their lead through a Jorginho penalty after Pickford brought down the impressive Havertz.
With 10 league games of the season left, Chelsea remain fourth and in the last Champions League qualifying spot, only three points behind third-placed Leicester and four adrift of Manchester United in second.
Crucially, this victory takes the Blues four points clear of Everton in fifth and Carlo Ancelotti's side - who have a game in hand over Chelsea - will drop to sixth if West Ham avoid defeat against Leeds in Monday's late game.
Chelsea have not been beaten since a 2-0 loss at Leicester in Frank Lampard's penultimate game as manager on 19 January, with Tuchel yet to suffer defeat in 11 matches in charge.
The result leaves Chelsea, who have kept nine clean sheets since Tuchel took the job, on 50 points from 28 matches, four ahead of fifth-placed Everton and three behind third-placed Leicester City.