Cristiano Ronaldo was destined to be one of the best footballers in the world from the outset, according to former Manchester United team-mate Louis Saha.

The pair crossed paths during Saha's four-year stint at Old Trafford between 2004 and 2008, just as Ronaldo burst onto the scene following his arrival from Sporting CP.

The Portugal captain would go on to score 118 times in 292 appearances for United before sensationally returning for a second spell last month.

Ronaldo hit the ground running with a brace against Newcastle United – the only team he has a Premier League hat-trick against – in his first game back at the club last weekend and was also on target in a 2-1 Champions League defeat at Young Boys on Tuesday.

Saha said he recognized Ronaldo was a special talent soon after he first joined United.

"I saw it straight away," Saha told Stats Perform. "When you realize that the guy at this young age can do what he was able to do after a few games you realise that the guy is just an animal of work as well outside of the field.

"He is always obsessed about his game and how to improve straightaway.

"Maybe after a few months, he was already very confident in claiming that he was the best or he would be the best player in the world.

"So all those things were a big sign that the guy has something special in terms of skill, but [also] in terms of mentality and confidence.  All this make me fairly quickly believe that he had massive potential to be a top star.

"I'm not surprised from the moment he left United, I'm not surprised that he keeps doing it at this level because when you have the talent and you manage then to work harder than anyone who is a bit laborious, that's a fantastic combo."

However, it has not all been straightforward since Ronaldo's return, with 10-man United surprise losers to Young Boys on a landmark 177th Champions League appearance for the forward as he equalled Iker Casillas' record.

Ronaldo scored against his 36th different club in the competition on Tuesday, with 12 years and 132 days the biggest gap between Champions League goals for the same club in the competition's history.

But as Ole Gunnar Solskjaer's side failed to defend their one-goal lead, Ronaldo could be seen animatedly issuing instructions alongside his manager and Saha is interested to see how their new relationship will work.

"I think I will say that it could be strange for Ole in some way, more than for Cristiano because I think we have seen it all when he moved to [Real] Madrid and then to Juventus and improved as a superstar," he continued.

"So now to actually manage a player like that you played with, it must be a bit strange but at the same time, he's a very smart lad and at the same time, Cristiano is here to win.

"There is no conflict there. It's just about how to actually get the result they both want.

"I think he has the luxury to get to, let's say, the finished product in his hand. It's brilliant as a manager to be in that position and to [have] one of the best players in the world.

"So I don't think that is it any difficulty for him, just the players around will need to adapt. They need to play a certain way to optimise Cristiano Ronaldo, [he] is not 25 anymore. You have to play to a certain strategy."