The Fenerbahce manager is keen to capitalise on his counterpart's teething problems at Manchester United after the Portuguese's arrival brought an injection of excitement at Old Trafford after three frustrating years under David Moyes and Louis van Gaal
United started superbly but have only managed to impress in patches since their winning run ended, meaning they arrive in Turkey off the back of a frustrating goalless draw at home to Burnley.
Fenerbahce boss Advocaat could not believe United failed to convert any of their 37 attempts on Saturday and has no doubt it is merely a matter of time until Mourinho's side clicks.
"This man proved himself in all countries," the former Sunderland and Rangers boss said ahead of Thursday's Europa League meeting.
"If you see how many prizes he has won, that is almost unbelievable
He is not a magician
"There are so many good players at United, which is good on one hand and on the other hand it makes it difficult to find the real right line-up
"But it is a matter of time that he knows that, but quality-wise if you have six players like Manchester United it is still difficult to find - is it (Anthony) Martial, is it (Marcus) Rashford, is it (Wayne) Rooney? It's quite difficult.
"But I am sure that they will play for the first place, no doubts about that, and they will start winning games as well, and (Zlatan) Ibrahimovic will start scoring as well because that man knows how to score.
"At the moment not everything is going the right way, but see how many chances they have got last Saturday.
"If you don't create chances, that's a different story but they had so many chances last Saturday it was unbelievable they did not score.
"There is no reason to be worried about the team and about the manager."
Advocaat witnessed first-hand just how clinical United can be when things click into place a fortnight ago.
Paul Pogba's brace along with efforts from Anthony Martial and Jesse Lingard secured a 4-1 win at Old Trafford, with Robin van Persie netting a consolation at his old stomping ground.
The Dutchman netted twice in Sunday's 5-0 league win against Karabukspor and is expected to feature again on Thursday evening, when Advocaat is expecting around 45,000 fans at the imposing Sukru Saracoglu Stadium for the Group A clash
"We always go out in a game to win that game, play out of an organisation that we can stop the opponent, like United, and when we have the opportunity to attack, we will attack," the Fenerbahce boss said.
"But we play against Manchester United
I told you before this is a great team with great players, so in that way we controlled the first half hour (at Old Trafford) because of the way we played.
"If we did it differently, then they have too much quality to punish you and they did it in five minutes with two penalties and the game was over.
"Tomorrow in a home game is different, with the fans behind us
We have seen against Feyenoord that can help."
Source : PA
Source: PA