Kyle Lowry says the reaction of some Toronto Raptors fans to Golden State Warriors star Kevin Durant's latest injury setback was unacceptable.

Durant was helped off after damaging his Achilles in the second quarter on his return from a calf injury in Game 5 of the NBA Finals on Monday.

Although many Toronto supporters applauded Durant when he made his way off court, there were also cheers when he went down in pain.

Raptors guard Lowry said there can be no repeat of the reaction to Durant's misfortune after the Warriors reduced the deficit to 3-2 with a 106-105 victory at Scotiabank Arena.

"I don't think the fans knew the significance of the injury," Lowry said. "They kind of just seen he went down. In this league we're all brothers. 

"At the end of the day, we're all brothers and it's a small brotherhood and you never want to see a competitor like him go down. You don't know what the circumstances are.

"We don't want anything to ever happen like that. We don't know what's this or that. We don't want that type of stuff. 

"And it didn't change much emotionally. It was just after he went down he went down, and we got on and finished the game."