Sundowns signed the 21-year-old forward on a five-year deal from Egyptian giants Al-Ahly in August.
Mahlambi, who burst onto the PSL scene with Bidvest Wits in 2015, struggled for game-time in the year he spent abroad.
He has since scored once in five appearances for the Absa Premiership champions this season.
"Phaka is 21 years old," Mosimane said.
"He is full of speed and full of energy. He reminds me of when I got Percy and Khama, I still had to work on them.
"I told him Keagan [Dolly] left at 23 years old, Percy left at 23 [Ed: 24] years and I still have two years to fix a lot of mistakes.
"He is a raw talent, he missed a lot of steps. He has talent and potential but is still a little bit erratic. He could be better.
"He has speed, that's what we need at Bafana Bafana. He is a good prospect. We have a good team in Bafana with the young ones."
Sundowns, in eighth spot on the table with 11 points from seven games, next visit Chippa United at Sisa Dukashe Stadium in East London on Saturday.