The former Werder Bremen, Borussia Dortmund and Bayern Munich midfielder has been out of action since late August because of a hip injury and managed just 20 appearances for the Reds but will be fine to start the next campaign as the Canadian club looks to atone for a poor 2012.
"I spoke to him this morning," Mariner said. "The surgery went well, everything's fine and dandy.
"I told him what he needs just to get himself back. Like I said to all the players, we need to hit the ground running next season. Don't expect the preseason to get you fit everybody's under no illusions and [Frings is] no different."
And Mariner made it clear that former Germany international Frings still has the same attitude as when he first arrived at Toronto in June last year.
"He absolutely wants to be back," Mariner added. "He texts me before games and after games. He actually said to me the last time I saw him in Toronto 'coach, I'm going to give everything I've got. I want to go out on a high.'
"He's got a lot of pride and he wants to go out on a high and I'm more than willing to accommodate that."