Arsene Wenger always knew he would shift the Premier League title battle in favour of Manchester United when he let Robin van Persie leave Arsenal for Old Trafford.
United manager Sir Alex Ferguson put in a personal call to Wenger as he aimed to push through a £24million deal and beat bitter rivals Manchester City to the signature of the Dutchman.
City boss Roberto Mancini claims his side were "very close" to landing Van Persie, who has gone on to prove his worth with 20 goals already this season as United opened up a healthy lead at the top of the table.
Wenger was in no doubt that whichever of the Manchester clubs landed the Arsenal skipper would be in the driving seat for the championship.
"It was a very professional phone call (from Ferguson) and there was more than one. I will tell you the rest another day," said Wenger, whose side host City on Sunday.
"You know when you sell Robin van Persie to Manchester United, that (they lead the league) will be the case.
"Robin is one of the best strikers in the world and you know he will score goals for them."
Wenger added: "If he went to City he would have been just another striker in a bunch of world-class players."
Van Persie chalked up his 20th of the campaign when he came off the bench to net a superb stoppage-time equaliser in United's FA Cup third-round tie at West Ham, while his brace at Wigan in his previous league outing helped keep United seven points clear of City.
Wenger was always confident the 29-year-old could maintain his form from an outstanding final campaign with the Gunners.
"Robin is at the peak of his game. He has a high level of confidence in his qualities and knows his game well," Wenger said.
"He is more patient today than he was five or six years ago, now he can stay up front.
"Sometimes in games you don't see him for 20 minutes, but he knows he will get a chance at some stage and that he will use it.
"Before he always came back in midfield, but now he stays there and uses his killer instinct much better."