Frances Tiafoe was two games from reaching the fourth round at Wimbledon before succumbing to Karen Khachanov. (Matthew Stockman/Getty Images)

A jubilant Frances Tiafoe walked into the stands at Smith Center on Monday morning with a grin, a black tennis bag slung over his shoulder and a loud message for his World Team Tennis teammates practicing on the multi-colored court below.

“Yeah, Kastles!” he bellowed at Madison Brengle and Christina McHale, giggling as Brengle mis-hit a ball in surprise.

Tiafoe had plenty to be happy about Monday. Not only did he win a tense super tiebreaker Monday night to help the Washington Kastles clinch their home opener, 21-20, against the New York Empire and improve to 2-0, but he did so having reached a career milestone earlier in the day. Tiafoe cracked the top 50 in the world singles rankings for the first time, landing at No. 45 following his third-round exit at Wimbledon on July 7.

“I feel like I’m playing the best tennis of my career, like I can beat anyone on any given night,” Tiafoe said. “I’m definitely high on life right now.”

The 20-year-old sees the upcoming hard-court season and has nothing but positive thoughts despite a painful end to his Wimbledon tournament. With a spot in the round of 16 in sight and two games from victory at the All England Club, Tiafoe lost to Russia’s Karen Khachanov in five sets in a breakdown he later blamed on stomach pains.

Tiafoe described the loss as a valuable lesson that only will assist his ascent. He has had a breakthrough year so far, claiming his first ATP title in Delray Beach, Fla., in February, where he became the youngest American ATP champion since a 19-year-old Andy Roddick won in Houston in 2002. At Wimbledon, Tiafoe notched his first Grand Slam victory against a seeded player when he upset No. 30 seed Fernando Verdasco in the first round.

But when leading Khachanov, he panicked like he never had before in his career. After debriefing with his coaches, he knows now he likely didn’t eat as much as he should have during the match. He should have slowed down and called the trainer rather than try to power through stomach pain. He should have put a potential fourth-round match against Novak Djokovic on Centre Court in the back of his mind.

Tiafoe said he’ll be better able to handle future big moments. This summer, his hard-court schedule includes tournaments in Atlanta, Cincinnati and Toronto in addition to Washington’s Citi Open.

“There’s so many more tournaments to be played. There’s so many positives to come out of the week, the whole grass-court season,” Tiafoe said. “All in all, I hated playing on grass until this year, and if you watched me play, you’d have thought I grew up on it I was so comfortable.”

On Monday night, he played in the first of the Kastles’ seven home matches with high confidence.

In addition to Tiafoe — who is in his second season with the Kastles — the team will feature Venus Williams, Naomi Osaka and the decorated doubles pair Bob and Mike Bryan in different matches throughout the summer as Washington aims to capture its seventh World Team Tennis title. Williams, in her seventh season, is scheduled to play July 25 and 26, and Osaka, in her Kastles debut, is scheduled to play July 28 before she competes in the Citi Open.

The Bryan brothers return to the Kastles for their third year following Mike’s championship at Wimbledon with partner Jack Sock for his record-tying 17th career Grand Slam men’s doubles title.