There's no timetable for his return, and the MLS team said he may need to wear a protective mask when he does come back.
Frei left Saturday's game against the Columbus Crew in the first half following a collision with Crew striker Ryan Finley.
The Toronto 'keeper, who had cleat marks visible on the side of his crooked nose at Sunday's training session, said he considered approaching the referee at halftime to point out what he believed were several fouls that weren't called, including the tackle that put him out of the game.
"He didn't really get the message out that in the end you have protect the players, and it came down to mine. (Finley) put his boot in, my face against his boot, obviously he's going to be the winner," Frei told reporters. "It is what it is."
Frei, who didn't participate in Sunday's training session, said he didn't regret putting himself on the line in a pre-season game.
"I knew I had to go in with my head, I could have gone in with my leg but I knew that wasn't going to be allowed, and he decided to go in with his leg. That's just the nature of the sport," Frei said. "Absolutely I need to put myself on the line. You play the way you practise, if I'm not going to go out in a game like that who's to say I can do that in real match?
"I'm actually excited about the fact I went for it. It shows I'm not afraid, knew it was going to be painful as soon as I saw him going in with his boot."
Frei was hurt in his first outing since last March, when he injured his leg and ankle in training.