"Frustration. I thought it was a bad call. Combination of both," said DeRozan when asked about his ejection, according to ESPN's Ohm Youngmisuk.
The four-time All-Star was whistled for his fourth foul of the game with 5:01 remaining in the fourth quarter and San Antonio trailing 110-92 against the Denver Nuggets.
He finished with 19 points, five rebounds, five assists, and two turnovers on 7-of-13 shooting in 34 minutes of action in an eventual 117-103 loss.
Game 5 goes down at the Pepsi Center on Tuesday with the first-round series locked at 2-2.