The Cavaliers estimated the three-point specialist would be sidelined one to two weeks.
The Cavaliers trail, 3-2, in the best-of-seven Eastern Conference semifinal series and could be eliminated tonight.
Gibson emerged as a star for the Cavaliers with a career-high 31 points, including 19 in the fourth quarter, when Cleveland clinched a spot in last season's NBA Finals with a Game 6 victory over Detroit in the conference finals.
Detroit point guard Chauncey Billups proclaimed himself ready for Game 1 of the Eastern Conference finals after going through a full workout for the first time since a strained right hamstring early in Game 3 cost him the final two games of the series with Orlando.
"He went through the whole practice, full contact," Coach Flip Saunders said. "He would've played today. He looked good in practice."
Billups said he can't sprint straight ahead as well as he'd like, but was encouraged with his health after scrimmaging longer and harder than he expected to be able to do.
If Boston eliminates Cleveland tonight, it will host the Pistons on Sunday in Game 1 of the conference finals. If the Cavaliers extend the series to a Game 7, the next series will likely start Tuesday night.
Houston Rockets backup center Dikembe Mutombo, who has considered retirement for the last two seasons, said he has decided to return for an 18th season.
Mutombo, a free agent who will turn 42 next month, averaged 3.0 points and 5.1 rebounds last season.
Mutombo's 3,278 blocked shots are second in league history, behind only Hakeem Olajuwon's 3,830.