Chelsea moved six points clear at the top of the Premier League as Cesc Fabregas’ first-half goal beat Sunderland at the Stadium of Light.
This is Chelsea’s 10th consecutive league victory.
Sunderland keeper Jordan Pickford saved from former Black Cat Marcos Alonso and Willian to prevent Chelsea from winning by a bigger margin.
The hosts, who had set up to try to nullify their opponent’s attacking strength, had few chances although they could have snatched a point in injury time but Thibaut Courtois superbly denied Patrick van Aanholt.
It was a hard-fought and important win for Chelsea after Arsenal slipped up against Everton on Tuesday and means Antonio Conte’s side will be top of the table at Christmas.