NEW YORK -- If the late Jimmy Van Alen hadn't invented the tiebreaker in the 1960s, Pete Sampras and Andre Agassi might still be playing.
Without the revolutionary scoring system, the longtime rivals would have been tied 24-all in the opening set 3 1/2 hours into their U.S. Open showdown early Thursday morning.
Instead, by taking three of four tiebreakers, Sampras won the quarterfinal epic 6-7 (7), 7-6 (2), 7-6 (2), 7-6 (5).
The match between the aged was a match for the ages, with all the necessary ingredients to make it memorable: a sellout crowd, the New York stage in prime time and the sport's most beloved elder statesmen rising to the occasion through four sets that couldn't have been closer. Neither player broke serve, meaning the set score was tied 24 times.
A spellbound crowd of 23,033 filled Arthur Ashe Stadium, and USA Network's telecast drew the largest audience in cable history for a tennis event -- 3.4 million homes. Agassi, 31, and Sampras, 30, agreed their 32nd meeting ranked among the most memorable.
"It all kind of lived up to the hype," Sampras said. "When we clash and we're both playing well, I think it's some of the best tennis in the game."
Agassi, a notoriously poor loser, this time was exceedingly gracious -- perhaps a reflection of his respect for Sampras.
"It was quite a powerful evening in many respects," Agassi said. "You're talking about a few points that separate a match like that, possibly one point."
By that slim margin, the 10th-seeded Sampras advanced for the eighth time to the Open semifinals for a rematch against No. 3 Marat Safin. When they met in last year's final, Safin won in a rout that sent Sampras spiraling into a slump from which he's just now emerging.