ES Setif left back Hachi trained with Sundowns in January, before signing on transfer deadline day.
The 27-year-old is already preparing for the PSL with friendlies against Young Africans and Simba.
Mosimane expressed his admiration for the North African player, who becomes the first Algerian to play in the PSL.
"We saw him when Setif played against us," said Mosimane.
"We saw him during our match analysis, you know us, we pulled many. We pulled out against Setif and we identified him as a threat before the game. He was a threat during the game.
"It happened that he is free from Setif and also wants to play in the Champions League. Remember Setif are on suspension after the pitch invasion.
"It's a difficult one because to find a north African to come to the south and play, I think it will be the first or second one."
Thanks to Sundowns building their pedigree with the Caf Champions League title, they've been able to prize him from Algerian clubs.
The Brazilians first league fixture of 2017 is against Bloemfontein Celtic on February 8.