"He feels he's ready to go, he's trained incredibly hard, done his rehabilitation and worked closely with the NRL over their concerns.
"He's fit to play from round one, but accepted the NRL's decision that round three is the starting point - he'll live with that. We always thought he would be registered at some point, as close to round one as possible."
Foran was released by Parramatta in late July, after just nine games for his new club,
Mackinnon told Radio Sport that Foran was making "great progress" with addiction issues.
"He's raring to go - come round three he will let the country see that," said Mackinnon.
"There is a lot more to come in his career. He's a great kid, a very good player and I'm sure Warriors fans will get to see that over the course of the next season."
The Warriors threw the former Manly and Parramatta player a lifeline with a one-year deal, but the NRL sidelined Foran over concerns he was associating with undesirable gamblers and psychological problems.
Restrictions are in place over who he can associate with and Foran will undergo one further psychological test.