As he winds down his rookie season, the 19-year-old Learner Tien has compiled an intriguing résumé. What you see in Tien depends on which frame you choose. Start broad, then zoom in, and things get weirder as you go. When playing against all top 50 players this year, Tien is 9–14. Nothing earth-shattering, but very respectable for a teenager making the leap from the Challengers to the ATP level. What if we filter those results more? When playing against top 20 players this year, Tien’s record is 6–5. And then what if we limit to just those opponents ranked in the top 10? A blistering 5–3 record. This kid from Irvine, Calif., has accumulated more top 10 wins this season than anyone besides Carlos Alcaraz or Jannik Sinner. While Tien’s still working on week-to-week consistency against the tour’s rank and file, he seems to relish every chance to play against the very best players alive. And he’s beating them with one of the most oddly satisfying play styles you’ll see—a mix of sweet feel, sharp angles, lefty guile, and cool temperament.

This week in Beijing, Tien became the third-youngest ATP finalist of the season, behind fellow teen phenoms Jakub Mensik and Joao Fonseca, but on the right day he looks like he has more potential than either of those more-hyped peers. Bolstering his rep as a giant-killer, Tien moved through a brutal draw to get to the final of this 500 event: Francisco Cerundolo, Flavio Cobolli, Lorenzo Musetti, and Daniil Medvedev, though admittedly those last two opponents withdrew from third sets with injury, after Tien had already twisted the match in his favor. By the time Tien finished the championship match, he had gained membership in one of the fastest-growing tennis clubs in the world: people who have been mauled in straight sets by Jannik Sinner on a hard court. But everything that led up to that match was tremendously promising for Tien, who has just moved inside the top 40 and who, just a few weeks ago, hired as coach the greatest-ever Asian-American tennis player from Southern California: Michael Chang.

Just as it went with his coach, Tien’s stature is a common source of skepticism. At 5 foot 11 he lacks the long levers seen in most players at the top of the contemporary game. But the way that Tien is sometimes described, you’d think he was a modern-day Gilles Simon, massaging the ball around the court and playing a purely attritional game. Tien does relish the occasional long rally, but Simon is not at all what I see in him. He doesn’t have the face-melting, point-ending power of Sincaraz—a quality that his fellow teen Fonseca does, in fact, possess—but Tien loads up his ground strokes with plenty of pace and spin. To my eye, he’s got much more pop on his shots than he did this time last year, which is not all that surprising, given that he’s still growing up. (One measure of his youth is the fact that he has said he grew up watching Alcaraz, a quote that instantly reduced me to a heap of dust.)

What I’m most struck by is how mature his baseline game already is. He perturbs opponents of the highest caliber. Tien’s open-stance forehand I find impossible to read, and he seems so nonchalant when changing the direction of a rally. He opens up surprising angles early and often. Whenever he finds an opening, he ends points at the net with soft hands, which might portend a future that’s more all-court than counterpuncher. Perhaps these skills don’t inspire as much buzz as the quantifiable, raw power of Fonseca’s ball-striking, but it works all the same. (Right now, it’s actually working better; Tien just moved past Fonseca in the rankings.) It’s a savvy, supple baseline game that holds up well against big hitters—with Sinner the obvious and understandable exception. A year from now, I bet I’ll be favoring Tien over most opponents when caught in a neutral rally on a hard court. For evidence, just talk to Sascha Zverev, Daniil Medvedev, and Andrey Rublev, all of whom have lost to the new kid this season. (And if you do talk to them, you will hear Medvedev’s outstanding pronunciation of Le-ARN-er, which he has rendered somehow Italian.)

But it’s difficult to claw into the top 10 while needing to win every point from that neutral rally. Cheap and easy points make ATP life much more pleasant. As impressive as Tien’s ground strokes are, his serve is not yet doing him many favors. Often he’s spinning the ball in to get the point started. His coach is aware of this central deficit in Tien’s game and has said that they’re working on it. I recently asked the analyst Gill Gross about some great recent servers who are under six feet tall. It’s not the easiest list to populate, but we agreed that Mattia Bellucci, the 24-year-old Italian, is one intriguing outlier who can crack 130 mph despite standing just 5 foot 9. Tien, who already hits his spots quite well, has room for technical improvements on his serve that could squeeze out some more mph, according to Gross. It’s a testament to Tien’s skill as a returner and baseliner that he’s gotten this far on tour with his current delivery. He’s on the cusp of getting seeded at the Slams. Even a perfectly average serve would take him up another notch again. Leave it to Chang and his new protégé to prove that modest height is no death sentence in this sport.