Diego Costa
Costa to miss Maribor game. (Getty Images/Julian Finney)

Chelsea striker Diego Costa will not feature in his side's Champions League clash with NK Maribor, leaving his participation against Manchester United on Sunday in doubt.

Jose Mourinho confirmed the former Atletico Madrid star has not returned to training after missing the weekend victory's over Crystal Palace with a hamstring problem.

"It is the same problem that he has been having [in recent weeks]," Mourinho told a press conference. "He cannot play tomorrow but I don't have an idea how long he will be out for."

German international Andre Schurrle and Brazil midfielder Ramires did feature in Monday's training session but both are also unavailable for Tuesday's match, having also returned from international duty with problems.

"There are no laws to protect players [on international duty]," Mourinho added.

"It's just the mentality of the national teams and their coaches - it's up to them whether they want to take good care of the players or treat them in a selfish [way].

"I don't tell the players not to go or to pretend to have problem.

"We like our players to succeed in their national teams, but it's something that is out of our hands."

Mourinho has been particularly frustrated with Spain's handling of Costa in recent weeks. The 26-year-old, who has scored nine goals in seven league appearances, featured for his country twice during the international break but returned to west London unable to play.

Chelsea travel to Old Trafford this week to provide Louis van Gaal with his first test against one of the Premier League elite as United manager. Before that they host Slovenian champions Maribor, but Mourinho is not planning on resting too many names ahead of their trip to Old Trafford.

The Blues manager also confirmed John Obi Mikel will be unavailable for Tuesday's game after suffering a foot injury.