The last time Andre Agassi and Pete Sampras shared a court, it got ugly. Real ugly.
And they were well into retirement.
Agassi, offended that Sampras had the nerve to imitate his pigeon-toed walk during "Hit for Haiti" in Indian Wells, Calif., reiterated his belief the 14-time Grand Slam champion was a cheapskate by pulling out his empty pockets.
"I don't have any money," said a miked Agassi, who critiqued Sampras' tipping in his autobiography. "No, no wait, I got a dollar."
The embarrassment on Sampras' face was there for all to see.
Ahead of the Agassi-Sampras rematch at the BNP Paribas Showdown at Madison Square Garden on Monday, ESPN.com unveils the top 10 tennis rivalries of the Open era.
1. Andre Agassi versus Pete Sampras
Head-to-head: Sampras 20-14
As Agassi mentioned a few times, despite their years on tour, he and Sampras never bonded. They were different people and different on court, too.
Sampras possessed arguably the best serve in tennis history, including a fabulous second delivery, while Agassi was one of the great returners and baseliners.
More often than not, Sampras came out on top, especially when it counted, going 6-3 at majors. In Grand Slam finals, it was more lopsided 4-1.
2. Rafael Nadal versus Roger Federer
Head-to-head: Nadal 14-8
The mighty Federer was virtually unstoppable in his prime. His flowing strokes, all-around game and wonderful movement bamboozled the overwhelming majority of the field.
If Nadal hadn't come along, he'd have reached 20 Grand Slam titles by now -- and comfortably.
Nadal's heavily spun lefty forehand, though, is a shot Federer hasn't adequately dealt with on any surface. This includes grass, where in one of the greatest matches in history, the 2008 Wimbledon final, Nadal prevailed in five glorious sets.
With an aging Federer slowing down, it remains to be seen how many more times they'll meet in major finals.
3. Chris Evert versus Martina Navratilova
Head-to-head: Navratilova 43-37
In one corner was Evert, the girl-next-door sweetheart who wore down foes from the baseline.
In the other was Navratilova, an all-business, onrushing Eastern European built like a tank.
Their extensive rivalry lingered 15 years, and it was a tale of two halves. Evert won 22 of the first 26; Navratilova won 38 of the next 54.
Unlike Sampras and Agassi, they're the closest of friends, turning to each other in times of joy and sorrow.
4. Ivan Lendl versus John McEnroe
Head-to-head: Lendl 21-15
McEnroe famously quipped in a TV interview he had more talent in his finger than Lendl had in his entire body.
Maybe, but ice-cool Lendl got the better of "Super Brat" in Grand Slams and overall, and he handed McEnroe the most heartbreaking loss of his career in the 1984 French Open final.
McEnroe, desperate to win a maiden crown at Roland Garros, relinquished a two-set lead as his serve-and-volley game faded on the slow terre battue.
"Down deep, he knew he'd blown it -- for good," McEnroe's younger brother, Patrick, recalled in his book "Hardcourt Confidential."
Lendl, a loser in his four previous Grand Slam finals, got the monkey off his back. He'd finish his underappreciated career with eight Grand Slam titles.
McEnroe and Lendl feature in Monday's appetizer.
5. Jimmy Connors versus John McEnroe
Head-to-head: McEnroe 20-14
Lendl wasn't the type to get involved on court, rarely showing any emotion. But Connors, like McEnroe, was combustible, so it's no surprise the duo clashed on several occasions.
There were fireworks when the lefties played at the 1984 French Open -- in the semis -- and even more during an "exhibition" in Chicago in 1982.
Connors actually climbed over the net to confront McEnroe, doing some finger pointing in his face. McEnroe subsequently pushed Connors before the pair had to be separated by two burly officials. This was no charade.
6. Bjorn Borg versus John McEnroe
Head-to-head: Tied 7-7
Most fans remember the rivalry for one match, the 1980 Wimbledon final. They went to-and-fro in an absorbing fourth-set tiebreaker that lasted 22 minutes and 34 points.
Borg, the "Ice Man" who had bundles of female admirers, sought a fifth straight title; a young McEnroe was gunning for a first.
Borg, leading two sets to one, squandered five match points in the tiebreaker. Showing his mental toughness, though, he managed to prevail 8-6 in the fifth.
The inability to win the U.S. Open grated on Borg, with McEnroe inflicting defeats in the 1980 and 1981 finals. The latter proved to be Borg's swansong in Grand Slams.
7. Steffi Graf versus Monica Seles
Head-to-head: Graf 10-5
Graf, and her vicious forehand, ruled women's tennis until Seles, the unorthodox, hard-hitting, grunting Eastern European, showed up. In 1991, Seles ended Graf's 186-week reign as No. 1.
Seles went on to beat Graf in three of four Grand Slam finals from 1990 to 1993.
There should have been more occasions. Unfortunately, a deranged fan of Graf's stabbed Seles in the back at a tournament in Hamburg in 1993.
Seles eventually returned but wasn't the same. Graf downed her in consecutive U.S. Open finals.
Head-to-head: Serena 13-10
Accusations of predetermined outcomes clouded early matches between the sisters (greetings, Elena Dementieva). Those early duels often disappointed, not entirely surprising since they were teenagers when it all began in 1998 at the Australian Open.
As the years have advanced, especially in the past three, drama has been the norm. Take the 2008 Wimbledon final, for instance. Unfortunately for them, it was overshadowed the next day by Roger and Rafa.
Who could forget their quarterfinal at the U.S. Open months later? Serena, the younger, more emotional Williams, edged Venus 7-6 (6), 7-6 (7) in a classic that showcased their impressive athleticism.
9. Boris Becker versus Stefan Edberg
Head-to-head: Becker 25-10
"Boom Boom" Becker, ever the showman, loved the spotlight (and still does). Edberg, quiet and gentlemanly, was the opposite. When they met, it was similar styles on offer -- a ferocious battle of serve-and-volleyers.
Becker won seven of the first nine and the last eight, but Edberg had the edge in majors. Interestingly for a saga that began in 1984 and concluded in 1996, they contested a mere four matches at Grand Slams.
Edberg's five-set victory at Wimbledon in 1990, in which the Swede and German appeared in the final for the third straight time, was the pick of the bunch.
Becker revealed in his autobiography he took too many sleeping pills the night before, explaining his lethargic display in the opening two sets.
10. Lindsay Davenport versus Martina Hingis
Head-to-head: Davenport 14-11
One or the other held the year-end No. 1 ranking from 1997 to 2001.
Hingis' variety and court acuity left many an opponent exasperated at a time when bashing baseliners had begun to take over.
Davenport, among the powerful hitters, wasn't one of them. When there was a crucial tilt between the two, the Californian always seemed to raise her game, including in two Grand Slam finals. She held a 10-6 edge in finals overall.
Ravi Ubha is a frequent contributor to ESPN.com.