Casper Ruud has hit back at tennis podcast host Scott Barclay after the latter suggested John Isner was not an exciting player to watch in the wake of his retirement announcement.

Former Wimbledon semi-finalist Isner announced on Wednesday, August 23, that he would be retiring from the sport after this year's US Open. In an Instagram post, the 38-year-old wrote:

"There comes a time in every athlete's career that they have to decide to hang it up. For me, that time is now. I didn't come at this decision lightly, but I feel it is the right way to go. When I left the University of Georgia in 2007, there was no way I could have imagined playing 17 years on the ATP Tour.

"Of course, there are countless matches I wish I could have back, but I am proud of what I was able to accomplish. The journey was nothing short of incredible."

Following this announcement, Barclay, who is a co-host of the tennis podcast Murray Musings and a writer for Popcorn Tennis, suggested on social media that he thought Isner was not an interesting player.

"Be honest with yourself, did you ever rush home from school or work or wherever and sit down in front of your TV in excitement to watch a John Isner tennis match?" he wrote on X, formerly known as Twitter.

World No. 5 Ruud was quick to defend the American player, referencing some of Isner's most famous matches.

"Yes, I did, several times actually. When he was up 2 sets to 1 on Rafa at RG [Roland Garros] 2011, the longest match in history against Mahut at Wimbledon and when he won Miami open the last time it was played at Crandon park to name a few," he replied.

Isner made history at the 2011 French Open as the first player to take Rafael Nadal to five sets at the clay-court Slam, a tournament which the Spaniard dominated for years.

A year prior to that, Isner locked horns with Nicolas Mahut at 2010 Wimbledon in what became the longest match in history. It was so long that it had to be contested over three days, totaling eleven hours and five minutes.

Ruud also referenced the 2018 Miami Open final in his response, where Isner defeated Alexander Zverev to win the only ATP Masters title of his career.

Isner is now preparing to face Facundo Diaz Acosta in the opening round of the US Open.