Chelsea are now eight points clear of fifth-placed Tottenham thanks to a 3-0 win over 10-man Leeds to virtually seal Champions League qualification next season.
The Blues got off to the ideal start in the fourth minute when Mason Mount fired a first-time strike into the top corner beyond the reach of Illan Meslier.
And with the visitors continuing to pile on the pressure, Daniel James was shown a straight red card for reckless late challenge on Mateo Kovacic in the 24th minute.
Six minutes later and Lukaku had the ball in the net when he delicately lobbed Meslier, but it was chalked off for offside.
Chelsea started the second half on the front foot and Christian Pulisic extended their advantage in the 55th minute, drilling his low shot from outside the box into the bottom corner beyond a static Meslier.
And Chelsea wrapped up an easy win in the 83rd minute through Romelu Lukaku, who fired into the roof of the net from close range after a poor giveaway from Diego Llorente near the halfway line.