Winning without Costa delights Mourinho
The Spain international missed the trip to Selhurst Park with a long-standing hamstring complaint thought to be at the root of his absence.
Mourinho blasted the striker's national side for over playing him during the recent Euro 2016 qualifiers, but was left soothed as goals from Oscar and Cesc Fabregas secured a 2-1 triumph, in which Loic Remy proved a handful up front - drawing two bookings which saw Damien Delaney dismissed in the first half.
With Chelsea sitting pretty five points clear at the top of the Premier League, Mourinho is enthused by the progress being made by his players.
"Winning without Diego was great," Mourinho said.
"There is a general feeling that our team is improved because of Diego and Fabregas. And it's right and it's true and it's fair to say that.
"But at the same time this team had a big improvement. We can think the game, control the game, cope in different moments of the game in a completely different way.
"Last year my team was naive. We couldn't cope with certain moments of the game, so we've worked, worked, worked and at this moment I'm happy."
Chelsea captain John Terry echoed his manager's sentiments and believes the west London club's strength in depth earmarks them as potential champions.
He explained: "The one question mark people had about us was whether we could win without Diego.
"He's done so well that people wondered, if he was out, who could come in and do it.
"We can match everyone, I think. Our football speaks for itself.
"Last season people thought they could get in our faces and distract us. But we are as strong as anyone and hungry to win the league. The hunger is in the squad and hopefully that can see us through."