After spending the best part of half an hour lavishing praise on Sir Alex Ferguson before their first Barclays Premier League meeting tomorrow, Luiz Felipe Scolari undid all his good work with one throwaway remark. The mischievous grin on his face was enough to reveal that his observation that Cristiano Ronaldo could be playing for Chelsea next season was intended as a joke, although, given the uncertainty that the Portugal forward caused at Manchester United this summer, Ferguson is unlikely to see the funny side.

The United manager was sufficiently concerned to question Scolari's motives after the Brazilian was quoted as saying that Ronaldo should “follow his dream” during the summer, when Ronaldo was linked with a move to Real Madrid, and such suspicion could harden to fury, depending on which side of the bed in his Cheshire mansion the Scot gets out of this morning.

If Ferguson bites, Scolari will have done his job, succeeding in taking his opponent's eye off the ball before a match that, even this early in the season, United can scarcely afford to lose. Their post-match meeting in Scolari's office for a glass of French or South African wine - “I don't have any Brazilian and I know he doesn't drink Portuguese wine because he used not to have it with [José] Mourinho,” the Chelsea manager said in another joke with a jag - could be as tense as the match itself.

Scolari's observations on Ronaldo began as a paean of praise to a player he regards as a son, although he went on to show a sting in the tail. Mourinho made preliminary inquiries about signing Ronaldo midway through his first season at Stamford Bridge four years ago, only to be rejected by Jorges Mendes, his and the player's agent, and Ferguson would no doubt come up with a stronger response if an approach is made next summer.

“Cristiano will leave Old Trafford one day,” Scolari, the former Portugal coach, said. “He won't play 50 years for United. Maybe he'll play seven, eight or ten years in Manchester and then finish his career. Maybe he'll play to 35, another 12 years in Manchester. After that he'll finish. If he goes to another club, whether in one year or two years, I don't know.

“He's my friend, I like him as a father likes his son, but his life is his life. I spoke to him once or twice when I was with Portugal, but he had an agent, a mother, friends and is an intelligent boy. I don't know what happened this season or what will happen next season.

“Cristiano is one of the best three players in the world. When I was at Portugal, I had to choose three players every year [for the Fifa World Player of the Year award]. One year I chose Didier Drogba as one of my three. Another year I wrote John Terry. Another year I wrote Frank Lampard. Now these three players are with me and that's very good for me. Maybe next season Cristiano is with me. That would be very good. If he wants to change, I'll open the door to that.”

Ferguson is considering whether to give Ronaldo his first start of the season after ankle surgery in the summer, although Scolari has no doubts that he will play from the outset after coming on for the final half-hour of Wednesday's goalless Champions League draw at home to Villarreal.

Having recruited him to the Portugal squad at the age of 17, Scolari knows Ronaldo better than most and believes that he is showing sufficient maturity to captain his country. Ronaldo, 23, would do well to target José Bosingwa, an international team-mate, tomorrow because, for all the right back's flowing attacking play, he has not been tested defensively. “When I arrived in Portugal, Ronaldo was a kid,” Scolari said. “He was starting as a very good professional, but at that time he was already thinking about his future. He's improved very well in the five or six years since.

“Next season I can see him as a captain with Portugal, because people like him and he has the confidence for that. He's a very good man, helps the other players and has a good attitude on and off the pitch. I don't know if the word is correct, but Ronaldo has grown up, matured.

“I think he will start. My players are thinking that, if they play very well, they mark him. United have a beautiful team, a fantastic team, and this is a big game. The players are prepared for this.”

Scolari has a selection dilemma and must decide whether to risk Drogba and Michael Ballack from the start on their return from knee and foot injuries respectively. Such issues may have been playing on his mind as he subjected his players to another verbal tirade during training yesterday, accusing them of repeating the errors they made in the 4-0 win against Bordeaux in the Champions League on Tuesday by searching for glory with their passes instead of controlling possession.

“When I trained with them today, I said the same,” Scolari said. “You saw our mistakes against Bordeaux and in training we made the same mistake after ten minutes. I stopped training and said I want this, this and this. We need to keep the ball and stay in position. Against United, why is 10-0 better than winning 1-0?” It could almost have been Mourinho talking.