Coach Erik Spoelstra said after Thursday's workout that Herro is going through all the necessary steps, but he hasn't been able to clear the final hurdle with Game 4 against the Denver Nuggets scheduled for Friday night.
"This is just part of the process," Spoelstra said. "You have to go through stages. First part of it was just shooting, then movement, then contact versus coaches, and then the next level of contact in practice. He has not been cleared for a game, and he is still not cleared yet."
The Heat trail the Nuggets 2-1 in the best-of-seven series.
Herro, who broke his hand during Game 1 of the Eastern Conference quarterfinals against the Milwaukee Bucks on April 16, has been ramping up his workouts for more than a week.
"Obviously, he has been huge in what we have done all year long," Heat star Jimmy Butler said. "But I think his spirits are really high. He is doing everything that he can to come back and help. I don't know where he is in that process, but I see him working. I see him smiling. I see him being around the guys, which is good for him and even better for us.
"We want him out there competing with us. We always have. We always will. But whenever he is ready, he'll be back, and he will be better than ever."