Chelsea boss Jose Mourinho says his players will not underestimate NK Maribor in the Champions League.
The Blues host the reigning Slovenian champions on Tuesday night with the Portuguese fully aware of the strength of Ante Simundza's side.
"The results tell you a lot. When you don't lose at Celtic Park, when you don't lose in Gelsenkirchen, that tells you they're a difficult team.
"Their results away from home have been very impressive.
"They are still fighting for qualification, so we must go with the best we have."
Chelsea travel to Old Trafford this weekend but Mourinho says the focus is entirely on the Champions League game.
"I won't rest players. I don't have Manchester United in mind, I have Maribor in mind," said Mourinho.
"[Diego] Costa is not training because he is not in condition to do so.
"I have no idea how long he will be out. Tomorrow he cannot play. The weekend is not important right now - but he cannot play tomorrow.
"Mikel made a big effort to be available for the weekend. He came back from the national team with a foot problem. He can't play tomorrow."