Palace started the weekend in fifth place, and had been undefeated in six matches, but looked short of an attacking threat without injured midfielders Yannick Bolasie and Yohan Cabaye and striker Connor Wickham.
Chelsea’s players, on the other hand, appear revitalized and are playing with more freedom since Mourinho’s departure. No one more so than Costa, who set up the opener before getting the goal his all-round performance deserved.
The Spain striker ran onto Cesc Fabregas’ through-ball, cut in and squared a pass for Oscar to sidefoot home into an empty net. Fabregas, back from illness, formed an effective central-midfield partnership with John Obi Mikel, with Nemanja Matic dropped to the bench.
By then, Hazard had hobbled off with an apparent groin injury in the 16th minute in another blow to last season’s player of the year in English football, who is yet to score this campaign.
Willian has been Chelsea’s best player this season and the Brazil winger came into his own in the second half, doubling the lead in the 60th by rifling a rising shot into the roof of the net from 22 meters.
Willian then dribbled into the area and sent in a low shot that was only parried by goalkeeper Wayne Hennessey out to Costa, whose tap-in deflected into the net off Joel Ward in the 66th and sealed Chelsea’s biggest league win in almost a year.
“It’s unfortunate what’s happened,” Terry said, referring to Mourinho’s exit. “We feel like we’ve let everyone down. We are where we are, and slowly climbing the Premier League table.
“Guus has come in, picked things up and we’ve had to go again.”