"As I begin the next chapter of my life, I am looking for ways to pursue a career in business, specifically in real estate," Agassi, 36, said in a statement.
Having annoyed Nadal with an underarm serve at Acapulco, Nick Kyrgios doubled down with the tactic to win two points against hapless Serb Dusan Lajovic at the Miami Open and fire up a timeworn debate between modern fans and purists.
Defending champion Nadia Petrova was also shown the door in the quarter-finals of the German Open.
World number one Amelie Mauresmo won 4-6, 6-4, 6-4 to enter the semi-finals of the German Open.
More than 100,000 viewers voted in the contest, which was broadcast on ZDF television.
The defending champion lost to Russia's Nadia Petrova 2-6, 3-6 in the quarterfinal.
Serena Williams' memory is not as powerful as her first serve these days, although with so many achievements to recall it would be churlish to hold that against the American great.
Ailing knees, Father Time and even a resurgent Victoria Azarenka stand in the way of Serena Williams clinching her seventh Australian Open title and giving her one more shot at an achievement that would cap her storied career.
The real Serena Williams finally turned up at the French Open on Saturday in pursuit of a 22nd Grand Slam singles title but it was to no avail as she lost to a tenacious opponent who beat her at her own power game.
Serena Williams overcame a gritty challenge from unseeded Dutchwoman Kiki Bertens, winning 7-6(7), 6-4, to reach the French Open final, in Paris, on Friday. She will meet Garbine Muguruza, who reached her second Grand Slam final when she beat Australia's Samantha Stosur 6-2, 6-4 in the first semi-final at Roland Garros.
The Belgian injured her right leg in an awkward slide to the net during a third-round match against Switzerland's Patty Schnyder.
The Swiss outclassed American Lisa Raymond 6-2, 6-2 to reach the second round of the French Open.
The Russian battled back from a set down to beat French Open champion Justine Henin-Hardenne in the final.
Belgium's Kim Clijsters downed Maria Sharapova 6-3, 7-5 to win the Nasdaq-100 Open and claim her second consecutive title
Defending champion Serena Williams is the top seed in the women's draw. The American will be looking to equal Steffi Graf's Open era record by sealing a 22nd Grand Slam triumph.
The German goalkeeper is famous for his loud complaints and intimidation of opposing strikers.
Former Wimbledon champion Goran Ivanisevic has withdrawn from the grasscourt grand slam with a knee injury, organisers said on Sunday.\n\n
IMAGES from the matches played at the Miami Open on Thursday
The 26-year-old has already done enough to replace Tommy Haas as the\n\nGerman No. 1 when the latest world rankings are released on Monday.
Even the Parisian stormclouds cleared for Serena Williams on Tuesday, as the new mother's baby steps back to Grand Slam tennis became a stride into the second round of the French Open.
The 49-year-old had a hugely successful spell coaching former world number one Novak Djokovic from 2013 to 2016, a period in which the Serb won six of his 12 Grand Slam titles.
She becomes only the fifth woman to hold all four grand slam titles at the same time.
Floyd Mayweather Jr. preserved his unbeaten record as a professional with a unanimous decision victory over Manny Pacquiao of the Philippines in their welterweight mega bout at theMGM Grand Garden Arena on Saturday.
Seven-time grand slam champion Venus Williams advanced to the third round at Melbourne Park on Wednesday with a 6-3, 6-2 win over Stefanie Voegele but conceded she was still troubled by an elbow injury that forced her to pull out of the women's doubles.
Serena Williams had been a vulnerable conqueror at this year's majors, living dangerously and dicing with defeat on numerous occasions as she tried to become only the fourth woman to complete the calendar Grand Slam.
Here are some of those lucky celebrities who were invited to watch the Ladies Singles Finals.
The World No 1 becomes earliest qualifier for WTA Finals
Tennis fans -- commoners and celebrities -- took to Twitter to convey their congratulatory messages to newly crowned Wimbledon champion Serena, who claimed a record-equalling 22nd major title with a 7-5, 6-3 victory over Angelique Kerber in Saturday's Wimbledon final.
Date-Krumm, ranked 84, is a lengthy outsider to cause an upset against the dominant force in the women's game who is currently on a 33-match winning streak.
World No 2 Serena Williams shook out any cobwebs from four months away from tennis with a 6-3, 6-4 victory over France's Pauline Parmentier in the first round of the Auckland Classic on Tuesday.
Andre Agassi says that he and Novak Djokovic need to learn to trust each other if their partnership is to deliver results for the world number four.
Upbeat Venus ready to 'kill it' after loss to little sister
Serena Williams clinched a record 23rd grand slam title at the Australian Open on Saturday but spent most of the immediate aftermath talking about her older sister Venus.
Ana Konjuh was not a year old when Serena Williams played her first US Open match but both will be in the Arthur Ashe Stadium spotlight on Wednesday, with four gripping quarter-finals to take centre stage at the year's final Grand Slam.
Serena Williams won her eighth Miami Open title with little trouble, enjoying a 6-2, 6-0 win over Spain's Carla Suarez Navarro in just 56 minutes on Saturday.
What makes winning in Indian Wells and Miami difficult is the fact that the two tournaments are held back-to-back, over four weeks, and in completely different directions. No wonder they are sometimes labeled as the 'Fifth Major'.