The former Real Madrid star joined United for a British transfer record £60m last summer, and already has four assists and three goals in the Premier League for his new club.
And Toure believes Di Maria, along with the Real Madrid's capture of James Rodriguez from Monaco, was the best signing of the summer.
"I think it's definitely Di Maria and Rodriguez," Toure said as reported by the Daily Star. "Rodriguez was a fantastic one, and as well United with the move for Falcao, he is a great striker, unbelievable."
The City star also went on to praise one of his former teammates, Spain striker Alvaro Negredo. The former-Sevilla striker was allowed to return to La Liga by Manuel Pellegrini after an injury plagued season at the Etihad last term.
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"[Negredo] has had injury problems but he has been brilliant for us this last year and I think he will be a great move.
"We will be sad to see him go because he was one of our top strikers in the last year. Of course he had a couple of events and needed to go back to his country, but I think we are going to miss him a lot.
"And the fifth one, I think, one of my great friends, a good friend, Mario Balotelli, like my brother.
"I hope he is going to do well in Liverpool because he has been involved in a few problems in the past year. But I think this year he is becoming more mature and he can control all of that."
The Liverpool striker has endured a difficult start to life on Merseyside, in contrast to Di Maria, who has hit the ground running and has been one of the Premier League's best players so far this season.
He should feature as Louis van Gaal's side travel the short distance to the Etihad Stadium to face rivals Manchester City and Yaya Toure on Sunday afternoon. Radamel Falcao, another big summer arrival, should also return after missing the Chelsea game through injury.
Toure is a doubt for the game with a groin injury.