The Mavericks extended the series with an improbable 103-91 win at San Antonio Tuesday night without sharpshooter Dirk Nowitzki, who is hobbling with a sprained left knee.
He is likely out for Game Six as well, but his teammates proved Tuesday that they can win without him.
The Spurs could have clinched a spot opposite New Jersey in the NBA Finals, but squandered a 19-point second quarter lead and scored only 10 points in the fourth quarter. They now will have to beat the Mavericks in Dallas to avoid a Game Seven.
That is familiar territory for Dallas, who beat the Portland Trail Blazers and Sacramento Kings in decisive Game Sevens in their previous series.
"Maybe that's the way this is destined to go as well," said Dallas point guard Steve Nash. "We have some experience in Game Sevens, and we'd love to go back to San Antonio and play in another one."
The Mavericks rallied the 19-point deficit without Nowitzki, their leading scorer and rebounder, who played the role of cheerleader on the bench. They outscored the Spurs, 29-10, in the fourth quarter.
On the other hand, blowing big leads has been commonplace for the Spurs, who squandered double-digit advantages in five of their six postseason losses. They let an 18-point lead slip away in Game One of this series before winning the next three.
"We get a lead and then we don't play smart," said Spurs center David Robinson. "We haven't played 48 solid minutes yet in this series and it cost us twice."
Dallas has won five postseason games when facing a double-digit deficit. The possible return of Nowitzki would provide a major boost. He has missed the last two games.
"I'll put up some shots before the game and see how it feels," Nowitzki said. "If it feels OK, I'll play. If it doesn't, I won't."
When Nowitzki suffered the injury in Game Three, the Mavericks announced he would be sidelined 10-to-14 days.
Only seven of 149 teams have rallied from 3-1 deficits in the playoffs, although the Detroit Pistons did it in the first round this year against Orlando.
Michael Finley triggered the Tuesday, scoring 15 of his 31 points in the third quarter. He also had eight rebounds and five steals, and set a rare defensive tone for the Mavericks, who used a mixture of zones and switching man-to-man schemes to smother Tim Duncan.
He collected 23 points, 15 rebounds, and six assists, but got no help as the Spurs unraveled down the stretch.
"A lot of the guys were really frustrated Tuesday night," Spurs forward Malik Rose told the San Antonio Express-News. "And, usually, when those are the guys who get frustrated we tend to win. We're looking forward to coming back with a win."
The Nets will have had 10 days off by the time the Finals get under way next Wednesday in either San Antonio or Dallas.
New Jersey will be making its second straight trip to the NBA Finals after sweeping Detroit in the Eastern Conference finals. They have won 10 straight playoff games.