Robin Lopez and Kris Dunn exchanged words during the Chicago Bulls' practice on Monday in Santa Monica.
Lopez made an aggressive play on Dunn before the argument. Lopez left practice for 15 minutes to cool off before returning.
Chicago is on a seven-game losing streak.
"We had a very, very competitive practice," Boylen said. "I felt like we had some guys who are sick of not winning games."
Boylen said Lopez told him his discontent stems from not playing as many minutes as he had in previous seasons.
"I'm going to play some different people," Boylen said. "He has got pride and he wants to play, but he's all for the team and he understands. You don't always expect guys to be happy with their situation or their minutes or whatever. That's not part of this league. What's part of this league is you have to do what's best for the team. Rolo has always done that."
Chicago is trying to acquire at least a second round pick for Lopez's $14 million expiring contract.