Chelsea vs Maribor: Jose Mourinho promises to take Champions League clash seriously despite Manchester United clash looming

Chelsea face United on Sunday but Mourinho says he will not rest his key players against the Slovenian champions

Jose Mourinho during his pre-match press conference ahead of the Champions League tie with Maribor (Getty Images)

Jose Mourinho is thinking only of Maribor - and not Manchester United - as Chelsea embark on an important week.

The Premier League leaders face Slovenian opposition for the first time in Tuesday night's Champions League Group G clash at Stamford Bridge.

And on Sunday the Blues visit Old Trafford, where Mourinho's one-time mentor Louis van Gaal is now in charge.

Mourinho is not looking beyond Maribor, who he has no intention of taking lightly.

"I don't have Man United in mind. I have Maribor in mind," Mourinho said.

"I don't rest players. We must play with what we have, with the best we have.

"We are not going to concede any favour by resting people or changing the team, no way."

Maribor have drawn with Sporting Lisbon and Schalke in their opening two matches - Chelsea won in Portugal last time out, having opened with a home draw against the Germans - and Mourinho is not underestimating a team which reached the group stages at Celtic's expense.

He said: "We worked studying them and I'm happy because my players now have the feeling that they are a difficult opponent."

The major selection question is whether Didier Drogba or Loic Remy will start up front in the ongoing absence of Diego Costa (hamstring).

Mourinho recently spoke of his team being built with Costa as the attacking focal point and refused to discuss adjustments with a different striker in place.

"You speak about Diego, I don't speak about Diego," Mourinho said.

"I say to my players: 'I don't want to speak about injured players'.

"When somebody is injured I always look at it as an opportunity for another player. When he's not here, he's not here."

Mourinho is furious at Spain boss Vicente del Bosque after believing Costa's hamstring problem was exacerbated on international duty.

Instead of resting, the £32million signing from Atletico Madrid played almost every minute of the Euro 2016 qualifying matches against Slovakia and Luxembourg this month and Mourinho does not know if his top-scorer will be fit for Sunday's match at United.

"It's the same problem that he's having, but now an injury, not an 'almost injury'," Mourinho said.

"Let's see what happens for next weekend (at Old Trafford), but next weekend is not important. Important is (Maribor) and he cannot play."

Nigeria midfielder John Obi Mikel (foot) is again absent, while Brazil midfielder Ramires (groin) and World Cup winning Germany forward Andre Schurrle (illness) are also out despite training on Monday.

It is the situation regarding Costa which appears to be frustrating Mourinho most.

"It hurts," added Mourinho, who has not spoken to Del Bosque about Costa.

"You are not happy when you give players in good conditions and you receive the players in bad conditions.

Chelsea will be without Diego Costa, John Obi Mikel, Andre Schurrle and Ramires (Getty Images)

"I had managers with a very open communication, some others they simply don't care.

"Year after year after year, I don't have one single SMS (text message) or one single phone call.

"I don't say that communication is compulsory for the players to be back in good conditions. I'm not saying that.

"For example, I didn't speak with (Brazil boss) Dunga and Oscar, Filipe (Luis) and Willian came back in perfect conditions."

PA