Cristiano Ronaldo admits it is always "special" to return to Manchester United but has no plans to do his old club any favours on Tuesday, as Juventus aim to maintain their 100 per cent record in this season's Champions League.

The two heavyweights in Group H do battle at Old Trafford with the visitors boasting two wins from two so far in the competition.

Ronaldo was sent off in a 2-0 triumph at Valencia in the opening round of fixtures, meaning he missed the 3-0 victory at home to Young Boys while serving a one-match ban.

However, the forward is available again to face his former employers and, despite their indifferent form so far this term, is not underestimating Jose Mourinho's side.

Speaking to the media, he also issued a heartfelt message to his former United boss Alex Ferguson, who attended the Premier League fixture against Wolves last month after suffering a brain haemorrhage in May that required emergency surgery.

"It is special for me to return to Manchester," the Portugal international said at a pre-match press conference.

"Here I have many memories of victories and affection and in particular with Alex Ferguson, to whom I send a big hug. He is a person who helped me so much."

On the game, he added: "It's going to be a tough match. Manchester United are strong, but if we play the way that the coach wants we have a good chance to win the game.

"However, we can't underestimate our opponents."

While Ronaldo will undoubtedly be the centre of attention, the forward insisted his only focus is helping Juventus continue their push to qualify for the knockout stages.

The Serie A champions coped admirably without their big-name signing last time out in Europe, Paulo Dybala scoring all three goals for Massimiliano Allegri's side against Young Boys.

"The Champions League started two games ago, even if I'm returning now, it doesn't matter that I was sent off and then didn't play," Ronaldo said.

"We are in a great position and a win tomorrow will go a long way [to seeing us progress]."