The top seeds in the West will next face the Denver Nuggets or the Los Angeles Clippers, who are tied at 2-2 following a dramatic 101-99 win by the Nuggets.
The Clippers surged from behind to go 97-96 up – their first lead of the game – late on before tying it at 99-99 in the final seconds in Inglewood, California.
Nuggets star Nikola Jokic then missed with a second remaining, but team-mate Aaron Gordon had time to grab the rebound and beat the buzzer with a putback slam to win the game.
Game five takes place on Tuesday.
Earlier, Eastern Conference top seeds the Cleveland Cavaliers demolished the Miami Heat to take a 3-0 lead in their series.
The Heat’s 124-87 defeat was their worst play-off loss in franchise history.
Jarrett Allen scored 22 points and D’Andre Hunter added 21 as six Cavs players reached double figures.
Game four takes place on Monday.
Elsewhere, Stephen Curry scored 36 points to lift the Golden State Warriors to a 104-93 victory over the Houston Rockets, which puts the Warriors 2-1 up in the series.
They face each other again in game four on Monday.
