But the sparkle from Wednesday had gone flat by Saturday afternoon, and the windy conditions only added to the Olympic champion's woes. As befits one of the world's top showmen, Agassi was brilliant under lights in his grudge match against Muster, but under grey skies and heavy conditions, he could not turn on the style. He and Chang also had to follow an absorbing women's semi-final in which Steffi Graf beat Martina Hingis 7-5, 6-3, which meant the men got going in an atmosphere of maximum crowd movement and an air thick with the odour of hotdogs and spare ribs.
One game seemed to sum up the match. At 1-1 in the third set, Agassi worked himself to game point after trailing 15-40 and had an easy overhead to win the game. He belted it about three metres beyond the baseline, followed up with a forehand which hit roughly the same spot, and then saw a backhand pass from Chang sail into the corner for the decisive break of the third set.
Yet to concentrate solely on Agassi would be unfair to Chang, who now finds himself one victory away not just from his first Grand Slam title in seven years but also the top spot in the men's rankings. Standing in his way is Sampras who beat Goran Ivanisevic 6-3, 6-4, 6-7, 6-3 in yesterday's second semi-final. Sampras showed no sign of the severe dehydration that had him vomiting on court during his quarter-final match against Alex Corretja on Thursday night.
Chang, a super-fit intensely religious 24-year-old American of Chinese descent, stunned the tennis world in 1989 when he became the youngest ever winner of a Grand Slam tournament by winning the French Open at 17 years three months. He is tennis's biggest draw in Asia, where he has won 10 of his 26 career titles, and benefited from a controversial seeding upgrade at this year's US Open which makes him the No 2 ahead of his ranking of three. By reaching the final he has rewarded the US Tennis Association's faith in him.
He broke Agassi in the eighth game of an unremarkable first set, and once he had taken it 6-3 he got sharper as Agassi looked flat. Agassi said he felt he had lost the match by not responding to the conditions, but to a large extent Chang's precision groundstrokes didn't let him get into a groove.
Sampras also looked very different than in his quarter-final against Alex Corretja, which he won on a fifth set tie-break in a state of severe dehydration and suffering some stomach cramps. Two days off had got rid of any remnants of that draining experience, as he came out all guns blazing to beat Goran Ivanisevic 6-3, 6-4, 6-7, 6-3.
The direction was set in the first game, when Ivanisevic delivered three aces but still lost his serve. Despite 30 aces from the Croat in total, Sampras should have wrapped up the victory in three sets. He led 6-3 in the third set tie-break with two serves to come, but a dazzling back-hand pass from Ivanisevic followed by a double fault by Sampras set up a dramatic tussle, which Ivanisevic eventually took 11-9.
Sampras survived a break point midway through the fourth set as the match looked to have all the makings of going the distance, but a loose Ivanisevic service game at 3-4 let the champion back in, and he finished the match moments later.
In the women's event, Graf's win over Martina Hingis sets up the tournament's dream final between her and Monica Seles. Graf needed to draw on all her experience to thwart the challenge of the Swiss wunderkind. She survived five set points in a dramatic climax to the first set of their semi-final as Hingis threatened to pursue the generational change she started in the fourth round when she beat Arantxa Sanchez Vicario.
This time, though, experience triumphed over the exuberance of youth, and perhaps the women's tennis authorities will heave a sigh of relief that a 15-year-old will not be in a Grand Slam final. The WTA introduced strict age regulations two years ago to prevent girls playing professional tennis too soon - Hingis just escaped the new rules.