Chelsea star Diego Costa celebrates after scoring on his return against Hull
Hull started brightly but the game came to a holt after nine minutes following a nasty clash of heads between Gary Cahill and Ryan Mason.
And after a long time on the floor Mason left the field on a stretcher.
But that didn't deter Hull who continued to press as Harry Maguire tested Thibaut Courtois with a header.
Diego Costa scored Chelsea's first against Hull
Chelsea were slowly coming into the match and almost went ahead when Marcos Alonso's shot from the edge of the area deflected off Michael Dawson and forced Eldin Jakupovic into a fine save.
The Blues thought they had taken the lead when the returning Costa put the ball in the net, but his strike was ruled out for offside.
However, in the seventh minute of time added on Victor Moses found Costa, who fired low past Jakupovic and into the net.
Chelsea fans react to Diego Costa comeback
Sun, January 22, 2017
Click through the gallery for the best reactions as Diego Costa returns for Chelsea
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Click through the gallery for the best reactions to Diego Costa's Chelsea comeback
Gary Cahill got Chelsea's second against Hull
After the break Hull continued to make it an uncomfortable afternoon for Chelsea, with Michael Dawson forcing Courtois into a save.
But Chelsea put the game to bed when Cahill headed Cesc Fabregas's free-kick into the net.
The win moves Antonio Conte's men eight points clear at the top of the Premier League table.