Hard-serving Ivo Karlovic, 44, officially announces his retirement from tennis

Ivo Karlovic, the towering Croatian known for his booming serve, has officially announced his retirement from tennis more than two years after playing his last tournament match.

The 2.11-meter (6 foot, 11 inch) Karlovic said in a post Wednesday on X, formerly Twitter, that "I've had a very gratifying, unorthodox and long career coming from extremely humble beginnings, especially for a tennis player."

The 44-year-old Karlovic—he will turn 45 next week—played his last ATP match in a second-round qualifying loss at Indian Wells, Calif. in October 2021. His last Grand Slam tournament match was a first-round singles loss at the US Open about six weeks earlier.

"Some of you have noticed that it's been a while since I played a tournament and still ask me on a daily basis if and when I'll be returning to the tour," Karlovic wrote. "I'm sorry to disappoint, but with this letter, I want to make it official and finally announce my retirement."

Karlovic first made a name for himself in 2003 after coming through qualifying at Wimbledon and defeating defending champion Lleyton Hewitt in the first round at the All England Club. It was Karlovic's first match at a Grand Slam tournament and the result made Hewitt the first defending Wimbledon champion to lose in the first round since the start of the Open era in 1968.

Karlovic finished his 25-year career with eight singles titles and a record of 371 wins, 346 losses and $10.1 million in prize money. His highest singles ranking was at No. 14 in August 2008.

His best Grand Slam singles performance was at Wimbledon in 2009, when he advanced to the quarterfinals. He also won the Davis Cup in 2005 with Croatia when it beat Slovakia in the final for the country's first title.

His last tour win came in the first round of the the Hall of Fame Open in 2021 at age 42. He was already the oldest player to win an ATP Tour match since Jimmy Connors in 1995.

He finished his career with 13,728 aces, second behind John Isner with 14,470. Karlovic has the most aces in a best-of-three-set match with 45 at Halle in 2015 and two weeks later at Wimbledon became the only player to hit at least 40 aces in three consecutive matches.

Six-time Grand Slam singles champion Boris Becker was among those to congratulate Karlovic on X, calling his serve "the best in tennis."