DALLAS, May 29 (Ticker) -- In a fourth quarter for the ages, the San Antonio Spurs got their biggest boost from the aging Steve Kerr.

NBA TV highlights from Mavs-Spurs: 56k | 300k American Express Play of the Day: 56k | 300k Nestlé Crunch Time: Duncan and Rose 56k | 300k Dunk of the Night: Tim Duncan Speed Stick Never Quits Highlight: 56k | 300k Postgame news conference: Play

The 37-year-old Kerr nailed three three-pointers as the Spurs scored 23 straight points in the fourth quarter to defeat the Dallas Mavericks, 90-78, and advance to the NBA Finals for the first time since 1999.

"I was wide open. Those are shots I should hit," said Kerr, who won NBA titles with the Chicago Bulls from 1996-98 and with the Spurs in 1999. He nailed the winning jumper with five seconds left in Game 6 of the 1997 Finals over the Utah Jazz.

San Antonio, which won the 1999 title, hosts the Eastern Conference champion New Jersey Nets in Game 1 of NBA Finals 2003 at the SBC Center on Wednesday.

It will be the first NBA Finals matchup between two former ABA teams.

With Tim Duncan struggling and Tony Parker playing with a stomach flu, the Spurs looked flat and trailed by as many as 15 points in the third quarter and 71-58 after a jumper by Nick Van Exel of Dallas with 10:53 to play.

But after Duncan made 1-of-2 free throws 13 seconds later, the Spurs' wing players got hot from the outside. Manu Ginobili nailed a three-pointer and Stephen Jackson made back-to-back shots from beyond the arc to pull San Antonio within 71-68 with 8:53 left.

"Stephen kept us from falling down the hill totally," Spurs coach Gregg Popovich said. "He showed good choices. He made some threes, penetrated and pulled up, did a good job in that sense. He was very important in keeping us rolling."

"That's just me, I am aggressive," Jackson said. "If they are going to take away Tim, then someone else is going to have to score, so I just stepped up and took the shots with confidence, and I was able to knock them down tonight."

Kerr -- the NBA career leader in three-point accuracy -- then tied the contest with a three-pointer with 7:12 left, added another to put San Antonio ahead for good, 74-71, with 6:28 left, and connected on a third shot from outside the arc with 5:14 to play to make it 79-71.

Ginobili capped the incredible 23-0 burst with a pair of free throws with 3 1/2 minutes to go to give San Antonio an 81-71 advantage.

"I don't know what to tell you other than we were playing so well for so long and then bottom just dropped out," Mavs coach Don Nelson said. "The fourth quarter we couldn't get a shot to go in. I think they turned it up to a different level. It was amazing."

The Spurs outscored the Mavericks 34-9 in the final 12 minutes, with Dallas scoring the last four points of the game in the final minute with the result no longer in doubt.

In Game 5 on Tuesday, the Spurs blew a 19-point lead and were outscored by 29-10 in the fourth quarter in a 103-91 setback.

Jackson scored a playoff career-high 24 points, Duncan contributed 18 with 11 rebounds and Malik Rose 12 and 11 for the Spurs, who won each of the three games in Dallas during the six-game series.

Kerr, who had scored just two points in 13 minutes in the playoffs, scored 12 in 13 minutes in Game 6.

"We obviously got a big boost out of Steve Kerr out there tonight, which is something that you don't plan on because it's tough to do that if you don't play," Popovich said. "He was great coming in. It was obvious that Tony was having a hard time, he was feeling badly. We mentioned to Steve that he needed to be ready, that he was coming in tonight. He was real ready and we were fortunate in that regard."

"I couldn't remember the last time I played," Kerr said. "It's been a long time, but tonight Tony was sick and the team needed me."

Parker was held scoreless in just 13 minutes of action, missing all five of his shots. "I feel good now," Parker said. "You get the victory you kind of forget (feeling sick)."

Van Exel scored 19 points and Walt Williams 17 for Dallas, which played its third straight game without injured All-Star forward Dirk Nowitzki.

"We have holes in our team, but those guys play and they found ways to win," said Nelson, whose squad won a franchise-record 60 games in the regular season to tie San Antonio for the best record in the league. "They found a way to blend together and to become one. That is what you want your teams to do."

Dallas held a 46-40 lead at the break and stretched its advantage to 63-48 on a layup by Steve Nash with 4:20 to play in the period. But Kerr entered the contest for the first time 36 seconds later and changed the tone of the game.

"It was definitely loud in there today, and those guys were running, knocking down shots and playing real well at the beginning," Jackson said. "We just wanted to keep our composure and not get caught up in their style of game. I think we did that in the first half. In the second half, we slowed down and started playing defense like we normally do, and it went in our favor."

"The combination of them turning their gear up to a different level, we couldn't go to a different level," Nelson said. "We were playing at as high a level as we could get it all game. When they moved it up and we couldn't go any higher, I think that really was the end of it."