Whiteside, 26, re-injured his already problematic right knee in the second quarter of Saturday's Game 3 when he fell to the court amid contact from Heat teammate Luol Deng and Raptors guard Kyle Lowry in Miami's 95-91 loss to Toronto. Whiteside did not return to the game, and an MRI on Sunday revealed he had a strained MCL in his right knee.
The Heat didn't initially set a timeframe for Whiteside's return other than listing him as "day-to-day," but Spoelstra ruled the NBA's leading shot-blocker out for Game 4 after the Heat's Monday morning shootaround. Spoelstra also said that Whiteside and the team have considered various treatment options but decided against pursuing season-ending surgery.
"Obviously, all of us were very concerned when we left the building [Saturday]," Spoelstra said Monday. "You try to stay positive, but you also are aware of the different scenarios there could be. It's a non-surgery option, which is the best option, considering everything."
Whiteside has not been made available for comment, although he attended the Heat's practice Sunday with his knee immobilized and was also receiving treatment during Monday's shootaround session. The Heat's team policy is typically to not allow a player to speak with the media unless he is practicing or available for game action.
Spoelstra said Whiteside was in much better spirits on Monday, but declined to offer a timeframe for when he might be able to return from the injury. Golden State Warriors guard Stephen Curry sustained a similar sprained MCL earlier in the playoffs and has been out the past two weeks.
Whiteside had been playing through two other ailments in his right leg: a strained knee he sustained midway through the Heat's victory in Game 1 last Tuesday in Toronto and a thigh bruise he suffered in Game 3 of the Heat's first-round series win against Charlotte.
"It's the same knee, but two different things that happened," Whiteside said after Saturday's injury. "One I could play through and this one I couldn't. As a competitor, you always want to be out there and try to help your teammates as much as possible. When that's taken away from you, that's really tough."
Whiteside has averaged 12 points, 10.9 rebounds and 2.8 blocks in 10 playoff games this postseason. The Raptors will also enter Game 4 without center Jonas Valanciunas, who was ruled out for the remainder of the series after he suffered a sprained ankle on Saturday.
Spoelstra would not reveal who he planned to start in place of Whiteside, although veterans Amar'e Stoudemire, Josh McRoberts and Udonis Haslem are among the options. Raptors coach Dwane Casey has said Bismack Biyombo would most likely replace Valanciunas for Toronto.
Whiteside, who has earned $990,000 in his second season with the Heat, will be a free agent this summer, and on the open market he could command a max contract worth in excess of $90 million over four years.