Returning Ronaldo out to heap pressure on old club United

Ronaldo made his name in Manchester, winning the first of his five Champions League and three Premier League titles under the tutelage of Alex Ferguson, for whom he still retains the highest regard.

"To return here to Manchester for me is a huge emotion. When we were drawn together I remembered the history I made here. I won all the trophies: Champions League, leagues, cups," said a smiling Ronaldo in a pre-match press conference.

"I remembered the incredible fans and a person that I don't forget, who was one of the people that helped me most, Sir Alex Ferguson."

However, Ronaldo also inflicted one of Ferguson's biggest disappointments.

Having swapped Manchester for Real Madrid for a world record fee in 2009, Ronaldo was given a hero's welcome in his only previous return to Old Trafford but ultimately scored the winning goal to edge a contentious Champions League last-16 tie in the Spanish side's favour in 2013.

That proved to be Ferguson's final European match, and in the legendary Scot's retirement, United have fallen on hard times in Europe.

In the five years since, Ronaldo has won the Champions League four times with Madrid, while United have won just one knockout tie in Europe's top club competition.

More than contenders

Both sides are on course to make the last 16 this season. Juventus top Group H with a perfect record from comfortable victories over Young Boys and Valencia and United have taken four points from a possible six against the same opponents.

However, in large part due to Ronaldo's talismanic status in the Champions League, it is Juventus, who paid Madrid 112 million euros ($129 million) for the 33-year-old in July, and not United, who are being touted as contenders to win the competition, even by the English side's own manager Jose Mourinho.

"As far as I'm concerned, Juventus are more than just a contender this season to win the Champions League," said Mourinho.

"They have a really special player (Ronaldo), who makes a real difference as well."

Top scorer in the Champions League for the past six seasons, Ronaldo has been made to wait to make an impact for Juventus. 

Sent-off just half an hour into his European debut for the club at Valencia, he also sat out a 3-0 win over Young Boys three weeks ago due to suspension.

"My last two months in Juve was amazing. Everything goes well, my adaptation goes well, and the team is amazing," insisted Ronaldo, despite the off-field turmoil.

A former American model Kathryn Mayorga, 34, has accused Ronaldo of raping her on June 13, 2009, just before he joined Real Madrid from United. Ronaldo has vigorously denied the allegations and has been backed by his new club.

"It doesn't matter if I play or get sent-off. The most important (thing) is that we have six points, we are in a good position and I'm glad to be back," he added.

The threat of a hungry Ronaldo is dangerous for Mourinho, who is still under pressure despite encouraging recent results.

United battled back from behind for a dramatic 3-2 win over Newcastle and a creditable 2-2 draw at Chelsea on Saturday, but are still languishing nine points off the top of the Premier League in 10th.

"I think the last games proved that we can play, press forward and we have players to make the difference," insisted United striker Romelu Lukaku.

"The challenge of tomorrow is to win the game against a really difficult side, but we'll do our best and see where we stand against one of the best teams in Europe.”