Whiteside was benched for the entire fourth quarter. He finished with 12 points, nine rebounds and three blocks in 25 minutes.
According to Dwyane Wade, Whiteside went into the locker room early because he had to go to the bathroom, per ESPN. However, the center didn't explain himself to head coach Erik Spoelstra.
"Probably extremely upset like we all are," Spoelstra said of Whiteside.
Whiteside also wasn't available to the media after the game, per David Furones of the Sun Sentinel.
"Everybody, if they're angry, frustrated, pissed, funnel it into the team until we get the changes that we want right now," Spoelstra added. "That's it. We have enough to be able to push this thing forward the way we want to. This lack of consistency is killing us right now."
Whiteside's role has diminished at times throughout the past few years, most notably in the playoffs this past spring. The center averaged only 15.2 minutes per game during the Heat's first-round loss to the Philadelphia 76ers.
Although Whiteside is making more than $25 million this season, his minutes continue to fluctuate, and he doesn't seem to be taking it well.