The 36-year-old Portuguese returned to the club he shone for during six medal-laden seasons on deadline day, joining from a Juventus in a deal that could reach 23 million euros ($A37 million) .

The veteran will be making his first appearance for United since joining Real Madrid in 2009, with Solskjaer confirming he will feature against Newcastle at a vibrant Old Trafford.

"He's been good," former teammate Solskjaer said of Ronaldo's early impact back at the club.

"Of course, we've followed his career from afar since he left here and I think everyone's very, very happy to have him back.

"He can speak for himself but he seems like he's happy to be back as well.

"The mood's been very good, he's worked well and we're looking forward to Saturday, of course.

"He's been having a good pre-season with Juventus, he's played for the national team, he's had a good week with us here.

"He will definitely be on the pitch at some point - that's for sure."

Old Trafford will be rocking as fans celebrate the return of a player who was reportedly edging towards a move to Manchester City until United swooped a fortnight ago.

Solskjaer said he could see Ronaldo playing into his forties, like fellow United great Ryan Giggs, who adapted his game to remain effective at the top level.

"Of course, Cristiano is a different player to the one who left but he's in such good nick still and he will be looking at the next few years to play as much as he can, to score as many goals as he can," said Solskjaer.

Anticipation is huge ahead of Ronaldo stepping out in a red shirt once more, when the returning hero will also be back in the number seven shirt after Edinson Cavani gave it up for him.

A former United captain is looking to spoil Ronaldo's big day, with Newcastle manager Steve Bruce now hoping they can act as party poopers.

"It's always going to be tough and obviously the added spice of Ronaldo coming back has added to it," the Magpies boss said.

Australian Associated Press