John Isner paid tribute to her compatriot Serena Williams, calling her the greatest of all time after she announced her retirement from the sport.
Isner was the No. 1 ranked American man for several years. He continued to wave the U.S. flag during a barren period for male players in the country, who had been used to champions such as Pete Sampras and Andre Agassi.
The huge-serving Isner came closest to reaching a Grand Slam final at the 2018 Wimbledon Championships. He lost a long five-set battle to Kevin Anderson in the semifinal at SW19.
Although Isner has enjoyed a stellar career, his achievements do not come close to matching Williams'. The former world No. 1 has won an incredible 23 Grand Slam singles titles since becoming professional.
Many fans had hoped Williams' return after a year out at Wimbledon would lead to more dominance of the WTA Tour, but the 40-year-old has decided it is time to move away from tennis and into other areas.
Williams will retire after the US Open. Isner posted on Twitter about how dramatic this year's US Open will be because of Williams' retirement and called her the GOAT.
"The US Open will be quite a scene this year as we say goodbye to the GOAT. What an amazing career that absolutely transcends the sport of tennis."
The six-time US Open champion is scheduled to play at the Cincinnati Open next week before her farewell at Flushing Meadows. She is out of the Canadian Open after losing to Belinda Bencic in straight sets in the second round.
Hopefully, Williams will play at a high level during the US Open. She deserves a fitting farewell to mark her legendary career and impact on tennis. Winning the title in New York seems like a tough ask, but it would be wrong to rule out the 23-time Grand Slam champion.