Agassi's Father to Son: Retire Now

It's his last tournament on the international stage, and, for now his hopes for the championship title are still alive.

After 20 years at the top of world tennis, 36-year-old Andre Agassi is fighting his way through the early rounds of the US Open in his last bid for a Grand Slam win.

But his father, Mike Agassi, says he should stop right now.

"I hope [Thursday] night was his last match," Agassi told ABC News in an exclusive interview.

"If it's up to me, I won't let him go to play [Saturday]. He hasn't talked to me, [but] that's how I feel about it. I don't think he should play."

Agassi fears that his son will do long-lasting damage if he continues.

"His retirement is overdue," he said, "not because of age. He's been overdue because of illness. His back hurts."

Discussing Thursday night's classic five-set match against Cyprus' Marcos Baghdatis, he said, "I saw him. He's leaning on one side, [and] I knew that he's in pain."

"I saw he's not moving as good as he could," Mike Agassi said.

It's been alleged that the Agassi men have had a strained relationship because Mike Agassi pushed his son too hard from a tender age -- a fact the father does not deny.

"I was maybe a little rough," he said.

But now, the father insists the two enjoy a strong bond.

"I have a very good relationship with him, a complex relationship," he said.

And, there's no doubt, he is still brimming with fatherly pride.

"He brought a new game of tennis," the father said. "He's known in every country in the world."

"Everybody knows him," Mike Agassi said.

"He's one of the most popular tennis players of the last 50 years. You couldn't ask for more. We're very happy. I'm very proud to be his father. And I'm sure that he's proud of us."