Klay Thompson insisted his injured hamstring was not an issue after producing a performance his Golden State Warriors coach described as "amazing" in Game 4 of the NBA Finals.

Having hurt his left leg during a series-levelling victory for the Warriors in Toronto, Thompson sat out his team's 123-109 defeat to the Raptors in Game 3 on Wednesday.

The five-time All-Star was back in action on Friday but, despite scoring a team-high 28 points, was unable to prevent the Raptors triumphing again, meaning Toronto lead 3-1 to sit on the verge of a first title in their history.

"It didn't affect me," Thompson told the media after playing 42 minutes.

"Like I said before, it's the Finals, it's a long season, you play a hundred-plus games, you're going to be banged up. But you've just got to dig deep.

"No one's going to feel sorry for you, so you just got to go out there, man up and play the best of your ability."

Golden State coach Steve Kerr praised both Thompson and Kevon Looney, who played in Game 4 despite dealing with a fracture near his collarbone.

"Klay was amazing, with a tweaked hamstring to do what he did," Kerr said. "Looney as well, coming in and playing 20 minutes given his injury status.

"So both those guys are ...they're warriors. No pun intended. They just compete, compete, compete, and I'm really proud of both of them.

"Both played really well, but again, it wasn't enough in terms of our team effort."

While both Thompson and Looney returned to action, Kevin Durant is still yet to be involved during the Finals due to a calf problem.

Game 5 of the series takes place in Toronto on Monday.