Michy Batshuayi and Fikayo Tomori sent Chelsea through to the FA Cup fifth round with a 2-1 win at Hull City.
An early opener from striker Batshuayi calmed any Chelsea nerves, before Tomori's header stretched their lead in the second half.
Hull's reply was a fortunate one, Kamil Grosicki's free-kick taking a giant deflection off Mateo Kovacic.
The hosts began to believe they could force a replay, but Chelsea withstood the late scare to clinch a place in the last 16 of the competition.
18 - Michy Batshuayi has been directly involved in 18 goals in his 18 domestic cup starts (FA Cup and League Cup) for Chelsea and Crystal Palace combined, scoring 15 and assisting three.