United have won only one of their last eight Premier League games - drawing six and losing the other 4-0 at Chelsea - leaving Mourinho's men 13 points off the summit, despite the Portuguese vowing to deliver the trophy this season when he was appointed.
Much of Mourinho's campaign has been spent bickering with "Einsteins" in the media, or the Football Association, who have handed the former Chelsea boss two touchline bans already this term.
But Pochettino expects a stern examination when he takes fifth-place Spurs to Old Trafford on Sunday, against a manager he says remains at the peak of his powers.
The Argentine told a news conference: "I like Mourinho and I have a good relationship with him.
"Many managers' behaviour is worse than his but because he is the 'Special One', there is more of a focus on him.
"The refs focus on him, the media focus on him.
"Other managers are worse than him but they do not get the attention because they are not the 'Special One' like him.
"He's the 'Special One' and always will be the 'Special One'.
"He's one of the best. In some periods in football, you struggle a little bit. It's not easy to arrive at a new club and settle your ideas, your philosophy.
"For me he was and is one of the best managers in football history."
"It's true that we have one day more to prepare than them," said Pochettino.
"It's true that for us last season and the season before, it was tough to play Thursday and Sunday.
"I don't remember in my two and a half years here that we have had the advantage of one day. But, when you play against a team like Manchester United they have the strong squad, always they can rotate players.
"That is their decision and we know that it will be a very tough game for us and Manchester United are a great team.
"I am sure that it will be a very competitive game."