Looney's return to the lineup came as a surprise, given that he suffered a nondisplaced first costal cartilage fracture on his right side during Game 2 and did not play in Game 3 on Wednesday against the Toronto Raptors.
The Warriors' medical team made the decision to allow Looney to play on Friday, but his 10 points and six rebounds in 20 minutes were not enough to help his team improve its fortune in the series, as Golden State fell into a 3-1 series deficit with a 105-92 loss.
"Kevon's going to give it a go tonight," Kerr said before the game. "So further evaluation, a second opinion, and then a lot of research and making sure that there's no long-term risk involved with him playing. And it all checked out, and he's dying to play, and so we'll give him a shot, and we'll see what he's got."
Looney has provided a stabilizing force for a Warriors group that depends on his presence off the bench. Veteran center DeMarcus Cousins struggled in Game 3 as he continues to recover from a torn quad injury suffered early in the playoffs.
"The guy's just tough," Kerr said. "He's tough, and he wants to play. And the injury is in an area where it allows him to move well enough to give it a shot to play."
Kerr said he did not believe Looney would take a pain-killing injection before the game.
As for Kevin Durant, the injured forward remained out for Game 4 because of a right calf injury, though before the game, Kerr left open the possibility that Durant could come back at some point in this series.
"He's not playing tonight," Kerr said. "We're hoping he can play Game 5 or 6. And everything in between I've decided I'm not sharing because it's just gone haywire. There's so much going on, and so it doesn't make sense to continue to talk about it. He's either going to play, or he's not. So tonight he's not playing."
Warriors All-Star swingman Klay Thompson played Friday after missing Game 3 because of a hamstring injury. Kerr noted that while Thompson did not have a specific minutes restriction, the training staff would be watching him closely to see how his hamstring responded.
Thompson ended up playing 42 minutes and finished with 28 points.
"Klay was amazing. With a tweaked hamstring to do what he did," Kerr said after Friday's loss. "Looney as well, coming in and playing 20 minutes, given his injury status. Both of those guys are warriors -- no pun intended. They compete, compete, compete. I'm really proud of both of them. They both played really well, but again, it just wasn't enough in terms of our team effort."