Pete Sampras & Andre Agassi's ex-rival now helping bring down Novak Djokovic at US Open after joining opponent Learner Tien's team in NYC

Pete Sampras & Andre Agassi's former rival, Michael Chang, joined Next Gen ATP star Learner Tien's coaching team ahead of the US Open. The American, who caught attention in this year's Australian Open for defeating Daniil Medvedev, will be facing a 24-time Grand Slam champion in the first round at Flushing Meadows.

Chang is a former world No.2 and holds the record for being the youngest person ever to win a Grand Slam singles title, by winning the French Open in 1989 at just the age of 17 years and 109 days. He started working with Tien a week before the Washington Open in July, and would be present with the youngster in the player's box at the Arthur Ashe Stadium on Sunday.

In an exclusive interview with ATP, Chang revealed that he was approached by Tien's coach, Eric Diaz, with the possibility of helping the 19-year-old and looks forward to a fruitful US Open run. With the youngster setting up a titanic battle against Djokovic in his first match at the New York Slam, he only had positive things to say.

“I like his draw. Obviously, Novak is one of the greatest players to play tennis, if not the G.O.A.T. himself. Learner has nothing to lose. He has everything to gain. Certainly, growing up, Novak would have been one of the great champions he has watched growing up,” continued Michael Chang. “For [Learner] to get an opportunity to play one of them is very special and let's not deny the fact that Novak is still playing unbelievable tennis.”

Chang hung up his racquet over two decades ago in 2003.

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Michael Chang's daughter will be competing at the US Open as well

Michael Chang's 14-year-old daughter, Lani, will be taking part in the US Open girls' event this year. Lani is the older of the two daughters of the 34-time ATP title winner. His younger daughter, Maile, born in 2013, is also training to follow in their father's footsteps and play on the pro tour.

Chang's wife is also a former WTA player, Amber Liu. Even though the American did not have an extraordinary pro career, she is known for her remarkable wins at the NCAA championships. Liu won the NCAA singles championships twice in the years 2003 and 2004, representing Stanford University.

Liu also won the Intercollegiate Tennis Association's (ITA) National Player of the Year award in 2003 and 2004, and was an NCAA Doubles Finalist in 2005. Liu and Chang married each other on October 18, 2008.