Former Chelsea player and manager Ruud Gullit has warned there is a big question mark hanging over returning Blues boss Jose Mourinho and his ability to bring success back to Stamford Bridge.
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Chelsea confirmed Mourinho's return to the club on Monday with the former Real Madrid boss agreeing a four-year deal at Stamford Bridge.
But Gullit, who managed the club between 1996 and 1998, believes Mourinho's second coming may not yield the same results as his first stint in charge.
"Is it a good idea for him? I don't know. There is the same chemistry between him and the fans, yes," the former Dutch international told the Daily Star. "But the coaches who are less expected to do something win everything, the big prizes, so it's a very difficult situation for him.
"He is one of the best coaches there is. But can he do it, can he do it again? We are going to see."
And Gullit was also worried that Mourinho's fractious last season at the Bernabeu had dented the former Porto and Inter Milan manager's greatest attributes.
"You have to wonder if he'll be different after Madrid?" Gullit said. "He was not as loved as he was in England, that's for sure.
"But what surprised me more was that Mourinho's biggest asset is his psychological work with his players. "He makes them win things for him but he couldn't do that with Madrid, and that was strange because it's his strongest skill.
"I think he will be very keen on doing well here but I just think it's the ones who are less expected to who end up winning the best prizes."
However, former Chelsea midfielder Michael Ballack believes Mourinho's retrun was a "fantastic decision" by the club.
"To have Jose Mourinho at Chelsea is a fantastic decision," Ballack told Sky Sports. "He is a great character and a great coach. Even at his age he has had unbelievable success.
"To go back to a club like this, it is never a bad decision. Chelsea are a fantastic club - they won the Champions League last year and this year the Europa League.
"The money will be right for him, the fans love him, he has a lot of English supporters, even if they don't support Chelsea.
"Altogether it is a great package for him."