Despite a rampaging start to life at Stamford Bridge that has garnered nine goals in seven Premier League appearance, Mourinho has regularly shown concern over the striker's ongoing hamstring complaint.
And after Saturday's win at Selhurst Park, where Oscar and Cesc Fabregas scored magnificent goals in either half for the league leaders as both teams played the second period with 10 men, Mourinho spoke witheringly regarding Costa's treatment on international duty with Spain.
The former Atletico Madrid player started both Euro 2016 qualifiers during the recent round of fixtures, playing a full 90 minutes against Slovakia before being withdrawn after 82 minutes of a goalscoring display versus Luxembourg.
"The only thing I can say is after [Chelsea's 2-0 win against] Arsenal he went to national team, he played two big matches against Slovakia and Luxembourg and became in condition where he's not able to play for this club," Mourinho told his post-match press conference.
"I think he'll be in great condition in mid-November to be back for the national team. That's for sure.
"Our medical department will take good care of him and he'll be in perfect condition.
"He will play for me when he's got free time from the national team."
There were certainly plenty of reasons for Mourinho to be more upbeat as Chelsea maintained their five-point lead at the Premier League summit and unbeaten record this term.
Cesar Azpilicueta was sent off for a rash 40th-minute lunge on Mile Jedinak but Palace's advantage lasted just three minutes as Damien Delaney picked up a second yellow card for pulling back Willian.
Before Fraizer Campbell struck in the 90th minute, Chelsea largely controlled Palace through long periods of second-half possession - the highlight of which was a sumptuous passing move crowned by Fabregas in the 51st minute.
Chelsea are certainly showing the form of would-be champions but Mourinho believes the competitive nature of the English top flight believes success is far from guaranteed.
"If we were in another league, another profile of league, I would say immediately 'yes we will do it'," he explained.
"In the Premier League the only thing I can say is that we can do it, but in the Premier League it's difficult to say we are going to do it.
"So many good teams, so many difficulties, a long way to go, very difficult runs in front of us - I don't want to say that (we will win).
"We are a better team than last season. There was a clear evolution in our team.
"The evolution is not just based on the fact that we bought two fantastic players [Fabregas and Costa], because today one of them was not playing and the team was fantastic the same way."
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