The Clippers' victory comes after some Warriors players admitted they were watching their potential second-round opponent, the Houston Rockets, in the days leading up to the fifth game of the series.
Williams and the Clippers, who picked up a 129-121 win Wednesday night at Oracle Arena, took exception to being overlooked.
"That's something they should focus on," Williams told reporters. "For us, our focus was to come in and extend the series and get another game on our home floor. It's their mistake for looking ahead. That's on them."
After the Warriors' loss in Game 5, Thompson admitted he was looking ahead to the team's next series. The Rockets closed out the Utah Jazz in five games Wednesday night.
"Yep, start with me. I was," Thompson said. "I thought we were going to come out and win tonight, but sometimes life doesn't go as planned. We're still in a great position with hopefully only 48 minutes left to close these guys out. They've been pesky. They've been tough, but now it's time to do what we do."
Williams had 33 points, 10 assists and four rebounds in 34 minutes off the bench. Danilo Gallinari scored 26 points on 9-of-22 shooting. Montrezl Harrell added 24 points and five boards.
Kevin Durant led the Warriors with a game-high 45 points on 14-of-26 shooting. He added six assists and six rebounds in 41 minutes. Stephen Curry had 24 points and four assists, and Thompson contributed 22 points. Draymond Green added seven points, seven rebounds and six assists.
The Warriors hold a 3-2 series lead over the Clippers. Game 6 is Friday night at the Staples Center in Los Angeles.