The Spain striker missed Saturday's 2-1 win at Crystal Palace in the Premier League and a hamstring injury has ruled him out of the Group G clash against the Slovenian champions at Stamford Bridge.
Costa has been outstanding since joining the London club from Atletico Madrid, scoring nine goals in seven top-flight matches despite not being fully fit.
Chelsea boss Jose Mourinho confirmed on Monday that his leading scorer is unavailable to face Maribor along with Ramires [groin], Andre Schurrle [illness] and Jon Obi Mikel [foot].
"It’s the same problem that he [Costa] is having. Now an injury, not almost an injury. He's not training because he's not in condition to do it." he said.
"Tomorrow he can’t play. Let’s see what happens next weekend, but next weekend is not important, what matters is tomorrow and tomorrow he can't play."
The Premier League leaders face Manchester United on Sunday, but Mourinho ruled out resting players with one eye on the trip to Old Trafford.
He said: "I don't have Man United in mind, I have Maribor in mind."
Chelsea top Group G after picking up four points from their first two games, with Maribor unbeaten following draws against Sporting Lisbon and Schalke.
Mourinho's in-form side have won their last five games in all competitions, but the former Real Madrid coach is not taking Maribor lightly.
"Maribor's results tell you a lot. Their results away from home have been very impressive. We have full respect for them." he said.
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