Unheralded bench player Lonnie Walker led a fourth-quarter rally as the Los Angeles Lakers defeated the Golden State Warriors to leave the NBA champions on the brink of elimination from the playoffs on Monday.

The 24-year-old Walker erupted for 15 fourth-quarter points as the Lakers completed a dramatic 104-101 victory to put them one win away from clinching the best-of-seven Western Conference second-round series.

Walker, who has struggled to establish himself since joining the Lakers on a one-year contract last year after battling a series of injuries, was mobbed by LeBron James and other Lakers teammates after the victory.

James, who scored 27 points in the victory, said he had urged Walker before the game to be ready to help out.

"I've been telling him 'Lonnie you stay ready. We're going to need you at some point'," James said.

"For him to be as young as he is, to have that professionalism, to come out and stay ready when his number was called — we don't win this game without Lonnie Walker tonight, that's for sure."

Walker said he had been primed to make a contribution.

"It means the world to me, truly," Walker said.

"By the grace of God, I was given an opportunity to play. Night-in, night-out I've been going to the gym, everyone's been telling me to stay ready — Bron, coach, all of them. So when the call came I was locked in the entire time."

The Lakers will take a 3-1 series lead to San Francisco for game five on Wednesday with the Warriors needing to win to keep the series alive.

For long periods of Monday's game it looked as if the champions were poised to square the series.