Dallas ? An unused player with four championship rings engineered an unreal turnaround that sent San Antonio into the NBA Finals for a chance at the franchise’s second title.

Anybody remember Steve Kerr?

They certainly won’t forget him in Texas after the Spurs defeated Dallas, 90-78, Thursday night to win the Western Conference finals 4-2.

It seemed like a desperate move when the Spurs inserted the 37-year-old guard into the game late in the third quarter while trailing by 15 points, but instead it ended up being a brilliant one.

Kerr, who had played only 13 minutes in the entire postseason, made four shots from three-point range and calmed a jittery team during a stunning 23-0 fourth-quarter run that ended Dallas’ season.

“I mentioned to Steve that he needed to be ready tonight, and he was real ready,” Spurs coach Gregg Popovich said. “It’s a fitting finish to what I thought would be the end of his career, but he told me we’re going to have to think about an extension or he won’t be available for the finals. And he said that with a straight face.”

Stephen Jackson added 24 points, making five of San Antonio’s 10 three-pointers, on a night when Tim Duncan was double- and triple-teamed constantly by Dallas’ collapsing zone defense.

The Spurs held Dallas without a point for more than eight minutes during the fourth quarter to turn a lopsided game in the Mavs’ favor into the exact opposite — a lopsided game that was all Spurs down the stretch.

San Antonio outscored Dallas 34-9 in the fourth and advanced to play the New Jersey Nets in the NBA Finals beginning Wednesday night.

dallas guard Steve Nash (13) drives past San Antonio guard Speedy Claxton. The Spurs advanced to the NBA Finals with a 90-78 win Thursday in Dallas.

Kerr had three of his 3-pointers in the backbreaking 23-0 run that turned a 71-58 deficit into an 81-71 lead.

With the Mavericks collapsing on defense around Duncan, the Spurs were forced to try to win it from long range. Kerr, the career leader in 3-point accuracy, was the perfect player to lead the barrage.

“I figured just let it fly and see what happens,” Kerr said. “I haven’t been a difference maker in a long time.”

All four of his 3s were of the wide-open variety, each hitting nothing but net. Kerr only got the chance to play because Tony Parker had a stomach virus and backup Speedy Claxton was ineffective.

Kerr, who won three NBA titles with Chicago and one with the Spurs in 1999, finished with 12 points, three assists and two rebounds.

“This is one of best nights of my career, ranks right up there with anything that happened in Chicago. There’s always a chance to have one moment, and tonight was one of those nights,” Kerr said.

Duncan had 18 points and 11 rebounds, Malik Rose scored 12 points and Manu Ginobili had 11 to help San Antonio overcome scoreless outings from two starters — Parker and Bruce Bowen.

Nick Van Exel had 19 points to lead the Mavericks, who were without 7-footer Dirk Nowitzki for the third straight game because of a knee injury.

Dallas missed seven shots and had six turnovers in the fateful 23-0 run.

“It was a matter of them turning their gear up a level and we couldn’t get any higher. That was the end of it,” Dallas coach Don Nelson said.

It seemed as though the Mavericks had broken the game open in the early part of the third quarter, quickly extending a six-point halftime lead into double digits and keeping it there for most of the remainder of the period.

Dallas scored the first six points of the third, the final two coming when Steve Nash got isolated at the top of the key against Duncan, drove around him and fed Raef LaFrentz for an easy layup.

An easy layup was what Duncan missed on the Spurs’ next possession, and a 3-pointer by Walt Williams got the lead up to 55-42. Claxton threw away passes on two of the next three possessions, then had his shot blocked by Michael Finley.

Popovich had seen enough and turned to his third-stringer, Kerr, who had played only 3 minutes in this series. Kerr hit his first shot, a 3-pointer from the corner with 1:38 left in the third, but more important was the calming influence he brought to the floor as he stayed out there for a nearly 12-minute stretch.

Ginobili’s 3-pointer early in the fourth was followed by consecutive 3s by Stephen Jackson to make it 71-68, and Kerr’s second 3 of the night tied it.

Another 3 by Kerr with 6:28 gave San Antonio the lead for good, and he added one more with 5:15 remaining.

“I’m 37. I’m slow. I’m not a very good defender. I’m in there to take the open jumpers,” Kerr said.

LaFrentz played Duncan to a draw in the first quarter with eight points and seven rebounds to Duncan’s 10 and six, and the score was tied 22-22 entering the second quarter after Raja Bell hit a jumper with 1 second left on the clock.

Dallas scored the first six points of the second quarter and held a lead through the rest of the half, opening its biggest lead — 37-28 — on a 3-pointer by Van Exel. Williams hit a 3-pointer with 6.4 seconds left before intermission to give the Mavericks a 46-40 lead.

The Spurs had as many field goals (seven) as turnovers in the second quarter, then had six of each in the third.

Notes: Parker played only 13 minutes, shooting 0-for-5. … Bowen was 0-for-3. … TNT broadcaster Mike Fratello dismissed an Internet report that he was close to taking the coaching job with the New Orleans Hornets. “I haven’t spoken with them for two weeks,” he said. TNT broadcaster Jeff Van Gundy said he spoke with Philadelphia 76ers president Billy King, with both men deciding the Sixers and Van Gundy would not be a good fit. Van Gundy said he feels it’s “50-50” whether he’ll coach anywhere next season, adding that the Cleveland Cavaliers have not offered him their job.