“One extra ball coming back, one extra ball,” Karen Khachanov said after needing three hours and 50 minutes and five sets to get past Learner Tien in the fourth round of the 2026 US Open. “He loves to play that defense outside the court, that’s why it makes it extremely tough.” That is the scouting report most opponents arrive at. Tien is a left-hander from Irvine, California, who makes people hit more balls than they want to, and in two seasons it has taken him from outside the top 200 to the top 15.
Irvine, the juniors and Kalamazoo
Tien was born on 2 December 2005 in Irvine. His parents played recreationally and he learned the game on community courts near the family home, coached mainly by his father, Khuong, until he entered the USTA’s player development programme at around 10 or 11, according to his ATP biography. His mother, Huyen, is a school teacher, and he has an older sister, Justice.
He reached No. 4 in the junior rankings and played two boys’ singles finals at the majors in 2023, losing to Alexander Blockx at the Australian Open and to Joao Fonseca at the US Open. With Cooper Williams he won the 2023 Australian Open boys’ doubles, beating Blockx and Fonseca in the final. He won the USTA Boys’ 18s National Championships in Kalamazoo in 2022 and 2023, each title carrying a US Open main-draw wild card, and spent one semester at the University of Southern California before turning professional in the summer of 2023.
Twenty-eight in a row
The breakout came in the summer of 2024, when Tien won 28 consecutive matches between May and July. The streak took in four ITF titles in Southern California and his first Challenger title, at Bloomfield Hills in Michigan. He won a third wild card into the US Open that August by winning the US Open Wild Card Challenge, and entered the top 200 the same month. He ended the year in the final of the Next Gen ATP Finals, where Fonseca beat him.
Medvedev at 3 a.m., and a first title
At the 2025 Australian Open Tien came through qualifying and beat fifth seed Daniil Medvedev in the second round in a five-set match that finished around 3 a.m. in Melbourne. The ATP says it made him the youngest man to beat a top-five player at the event since its rankings began in 1973. He reached the fourth round, where Lorenzo Sonego beat him, and entered the top 100. Six weeks later in Acapulco, again as a qualifier, he beat world No. 2 Alexander Zverev, the biggest win of his career by ranking. On grass in Mallorca that June he beat Ben Shelton, then ranked 10th.
He reached his first ATP final at the China Open in Beijing in September 2025, losing to Jannik Sinner, and won his first title in Metz in November, beating Cameron Norrie in the final. The ATP says he was the youngest American to win a tour title since Andy Roddick in Houston in 2002. In December he won the Next Gen ATP Finals in Jeddah, beating Blockx in the final, the first left-hander to win the event.
2026: Melbourne, Geneva and Montreal
Tien beat Medvedev again at the 2026 Australian Open, this time in straight sets in the fourth round, to reach his first Grand Slam quarterfinal, where Zverev beat him. In March he beat Shelton to reach his first Masters 1000 quarterfinal, at Indian Wells. On clay he reached the fourth round in Rome and then won the Geneva Open, beating Alexander Bublik in the semifinals and Mariano Navone 3-6, 6-3, 7-5 in the final. The ATP noted he was the youngest American man to win a tour-level title on European clay since his coach, Michael Chang, won Roland Garros in 1989.
In August he reached the semifinals of the Masters 1000 in Montreal, the youngest American Masters semifinalist since Roddick in 2002, according to the ATP, and rose to a career-high No. 12. At the US Open he beat Jakub Mensik 6-3, 1-6, 6-7(2), 6-3, 6-4 in a third-round match on Louis Armstrong Stadium that ran past 1 a.m., and lost the fourth-round match to Khachanov 7-5, 4-6, 6-7(6), 6-1, 6-4.
Playing style
Tien is left-handed with a two-handed backhand, which he names as his best shot, and hard courts are his preferred surface. He is listed at 1.80m. Chang, the 1989 Roland Garros champion, is the most visible name in his coaching team. The ATP lists among his good friends on tour fellow American Alex Michelsen.
Grand Slam record
- Australian Open: quarterfinals (2026)
- Roland Garros: third round (2026) [UNVERIFIED: Wikipedia infobox only; confirm on ATP player activity page]
- Wimbledon: second round (2025, 2026) [UNVERIFIED: Wikipedia infobox only; confirm on ATP player activity page]
- US Open: fourth round (2026)
Season snapshot — 20 September 2026
Ranked No. 13, with a career high of No. 12, reached in August 2026. Career ATP singles titles: 2 (Metz 2025, Geneva 2026), plus the 2025 Next Gen ATP Finals. Coached by Michael Chang.
Tien made his Davis Cup debut for the United States in Prague last weekend. He beat Mensik 6-2, 6-4 in the opening rubber, then lost the deciding fifth rubber to Jiri Lehecka 6-3, 7-5 as Czechia won the tie 3-2 and took the place in the Final 8 in Bologna. He plays for Team World at the Laver Cup at The O2 in London from 25 to 27 September, before the Asian swing and the Shanghai Masters.
This snapshot is dated and will change. The career record above does not.
