Pete Sampras and Andre Agassi, in what began as an attempt at levity during a charity doubles match, launched their legendary rivalry into uncharted waters over the weekend in Indian Wells, Calif.
With the one-set match even at 4-4 on Friday night, Sampras and Federer took a 40-love lead in the ninth game, with Sampras appearing to put a little extra on his serves.
All of the players were wearing microphone headsets.
"You always have to go get serious, huh, Pete?'' Agassi asked to the delight of a laughing crowd.
Sampras then double-faulted, and the show began.
"OK, Andre, I'll joke around a little bit," Sampras said, with a slight hint of sarcasm. "I'm going to imitate you."
For 15 seconds, Sampras mocked Agassi's pigeon-toed walk in a circle behind the baseline. Gathering himself to serve, he directed a broad smile at Agassi directly across from him.
But Sampras didn't stop there.
With racket in hand, he awkwardly pinched and rolled his shirt-tail inward in another apparent ribbing of Agassi.
"Say something, say it," Sampras then declared to Agassi, hands in the air, asking for a comeback.
"I'm waiting, I want to impersonate you," Agassi replied.
"OK, go ahead," Sampras said.
Agassi pulled out the fabric of his empty sweatpants pockets.
"I don't have any money," Agassi said, using his left hand to continue rifling through that pocket. "No, wait, I've got a dollar!"
In a biography released late last year, Agassi told a story in which a valet confirmed to him that Sampras had tipped him a dollar after they had eaten at the same restaurant, an establishment that was said to be in Indian Wells.
"It's all fun and games until somebody gets hurt, huh?" Agassi said.
Sampras then bounced a ball as he appeared to begin to serve.
But Agassi interrupted.
"Look at him, he can't help himself," Agassi said.
"This guy," Sampras chided in return.
Meanwhile, the two greats of the current era, Federer and Nadal, continued to wait out the awkward moment.
"This rivalry is intense, man," Federer said. "I mean, Rafa, start. Do something."
Sampras then resumed play.
But instead of hitting to the return court where Nadal awaited his serve, Sampras darted a shot right at Agassi, who was able to dodge the ball.
"It's all right, it's all right," Agassi said.
"That's the way you want to play it?" Sampras jokingly said.
"You know what, it's better than being a valet driver and you pulling up," Agassi said.
Sampras couldn't hide his look of surprise this time.
"Let's talk about our baggage," Sampras said. "Here we go. I'm a bad tipper. I'm sorry, Barack Obama."
Play picked up again, and Nadal's crosscourt, backhand return kept the game alive.
"Wow," Sampras said, continuing the verbal jousting with Agassi. "You got personal. You got personal with me."
"Nah, nah nah" Agassi said. "Everybody knows that already."
Sampras and Federer went on to beat Nadal and Agassi 8-6.
The $1 million fundraiser that also featured singer Tony Bennett was a sellout at the 16,100-seat Tennis Garden.
Information from The Associated Press was used in this report.