Chelsea insist there is nothing untoward behind Andre Schurrle’s recent lack of first-team minutes as the German continues his recovery from illness.
The World Cup winner, who has been restricted to just four Premier League starts this season, suffered a persistent infection in October and could not train regularly.
He was forced to withdraw from his Joachim Loew’s international squad earlier this month and missed a Euro 2016 qualifier with Gibraltar and a friendly with Spain.
Schurrle was even linked with a move to Borussia Dortmund as a makeweight in a deal for Marco Reus but returned to the Blues squad for the win over West Brom last weekend and was given a late run-out in the 5-0 rout of Schalke in his homeland on Tuesday night.
Mourinho says there is no issue with the winger and believes he will start to appear more regularly in the coming weeks as his fitness levels are back to their peak.
“He was very ill - very - in the national team,” Mourinho explained.
“He was back here and he took a good two weeks, because it was a bad one. I think that affected him a lot from a physical point of view.
“When he started training again he had a fragile body. So, as a consequence, a fragile brain.
“But now he's coming step by step. He was on the bench against West Brom, and played 15 minutes in the last match. Step by step.”
Young full-back Nathan Ake is the only absentee for the clash with Gus Poyet’s Black Cats, with Mourinho declaring star striker Diego Costa ready to play.
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