According to Metro.co.uk, Mourinho led the Blues to a clutch of trophies between 2004 and 2007, winning two Premier League titles, two League Cups and an FA Cup.
He returned to the club this summer, with fans hoping for repeat performance, but Gullit believes that is unlikely, the report said.
He said that he has doubts over Mourinho not because of his quality but because had doubts over if someone could go to a team a second time and achieve the same things.
The former manager said that it would be an unbelievable achievement if Mourinho proved him wrong because he doesn't see a second spell success happening. (ANI )