Andre Agassi serves to Florian Mayer at Flushing Meadow on Thursday. Agassi won 7-5, 2-6, 6-2, 1-0. (Reuters)

New York: Players, fans and television announcers all continue to marvel at the same wonder here at the US Open. They watch Andre Agassi, the oldest player in the men’s singles draw at 34, and see his feet dance, his ground strokes sizzle. They wonder about his legs, his shoulders and his flexibility.

“Physically,” former rival Jim Courier said, “you have to wonder how he can still do it at this age.” More intriguing, though, is why he still wants to.

Agassi advanced to the third round at the US Open on Thursday, winning two of the first three sets before his opponent, Florian Mayer, retired with a hamstring injury. On a day when the French Open men’s and women’s champions lost and blamed their defeats on fatigue, a bouncy, energetic Agassi advanced to the weekend for the 14th time in 19 US Open appearances.

He is considered a major threat to win here because he has maintained his foot speed, his reaction time and his legendary ability to return serve. He has also maintained his desire, which impresses peers most. “There are a lot of times when it sort of hits you, how long you’ve been out here,” Agassi said. “But I’m not retiring at the end of this tournament.... I still love what I’m doing.”

Whenever he does retire from the ATP Tour, he will take a long legend with him. He has won more than 60 titles, including eight Grand Slams. He helped reinvigorate the men’s game with his dynamic rivalry with Pete Sampras, who is a year younger than Agassi but has been retired for two years.

He was one of the game’s most recognised players as a long-haired, loud-mouthed 17-year-old and now he’s still one of the game’s most recognised players as a bald, mellow 34-year-old. His desire to win remains every bit as strong, he says.

“I love the challenge, and I want to win just as bad,” Agassi said. “You’ve got a lot of guys out here with a lot of weapons that they bring to the table. I enjoy that. It really keeps me going.”

Agassi’s life is filled with signals to retire. He’s married to former tennis star Steffi Graf, and the couple has two children. His main longtime rival, Sampras, is no longer playing.

Already at this US Open, Agassi has listened to two more younger players — Wayne Ferreira and Todd Martin — announce their retirements. Yet Agassi needs tennis and tennis needs him.

Agassi’s the most popular player in the men’s game, an ageing yet still graceful ball of energy with the singular ability to turn spectators into fans.

When he won a close first set Thursday, the polite Arthur Ashe Stadium crowd erupted. Fans did the wave. They sang Ole. They chanted Agassi’s name until a befuddled chair umpire asked them — no, begged them — to quiet down.

“To me,” Mayer said, “they seemed very loud.” They’ll only grow louder as this tournament progresses.