February is a sleepy phase of the tennis calendar. What better use for it than to showcase the future? Teens are making moves on the ATP tour this week, and it’s almost enough to start looking at Carlos Alcaraz—who retired with an ankle sprain in Rio but said he’ll be back in time for Indian Wells—as a grizzled old man by comparison. Soon enough he’s gonna be yelling at these two to get off his lawn (in southwest London).

This week in Rio, the 17-year-old Joao Fonseca got a wild card into the tournament that’s held just 10 minutes from his house, and he’s put it to good use. Fonseca, currently the No. 2-ranked junior, is not long for the juniors; no chance he delivers on his commitment to play at UVA this fall, either, because he seems ready for the genuine article. On Wednesday he became the first player born in 2006 to win a tour-level match. Which led me to wonder: How many players have ever won a bagel set in their second-ever tour-level match? Fonseca whupped his first-round opponent Arthur Fils—an immensely talented 19-year-old prospect in his own right—on a drizzly evening with a delirious home crowd, 6–0, 6–4. (On that note: Brazilian crowds make me feel like I’m watching gladiatorial combat, but in a good way. Someone should take the Miami Open out of that accursed parking lot and drop it somewhere here.)

Fonseca backed that up with a win on Thursday over Christian Garin, 6–4, 6–4, becoming the youngest ATP quarterfinalist in a decade, and there were a few shots in this one that made me consider calling the authorities. Forget the eye test, I swear by the ear test, and we’re getting some Jannik Sinner-ish readings on the monitors, though I suspect Fonseca is even further along developmentally than Sinner was at age 17. Technique is wonderful on both wings; racquet head speed is bonkers; winners are spurting out of nowhere. Serve is perhaps a little idiosyncratic, but the rest of the repertoire is so scary I’d be a little surprised if he wasn’t a top 10 dude by the age of 20. Next up on Friday is a winnable quarterfinal match against world No. 113 Mariano Novana. You’ll be seeing a lot of this kid, soon.

Elsewhere in auspicious wild-card news, the 18-year-old Jakub Mensik should thank a cool new ATP policy for his joy in Doha this week. The Next Gen Accelerator Programme, which sounds like a tool for particle physics, is actually just a way to boost good players under the age of 20. If you’re ranked inside the top 250, and there are three tour events happening in a given week, you can now get a wild card into a 250-level event (once) or its qualifying draw (twice). Mensik, who was ranked No. 116 in the world at the start of the week and has had some interesting wins over the past few months, signed right up. He said he picked Doha specifically because he got a free iPhone out of the deal. As an added bonus, he also got wins over three top 50 players, which he’d never accomplished even once before.

If Mensik only took out Alexander Davidovich Fokina in the first round, dayenu, but instead he kept going. I’ll leave it to the reader to decide how much it means for a player to beat Andy Murray at this moment in his career. While Murray appears to have developed an unseemly addiction to losing close matches—he will be reliving the botched gimme volley on set point in the first set—he did put up a tough fight, and it was high-level stuff from Mensik to win in three tiebreaks.

Even then, there’s a sizable gap between beating those two guys and beating Andrey Rublev on a hard court. The Rublev experience is difficult to simulate; the power of “bweh” must be experienced firsthand, as there aren’t many players maintaining that raw pace from first point to last. It’s the sort of tennis that tends to blow away an unprepared foe. Somehow Mensik stood on the baseline and tracked the ball as if he’d been practicing against the Rublev forehand his whole life. Mensik’s tolerance for long, punishing rallies is a testament to his very sturdy baseline game, and the 6-foot-4 Czech backed it up with an excellent serve, which Rublev didn’t manage to break once in the match. Mensik won 6–4, 7–6(6) and made his first ATP semifinal, where he’ll play Gael Monfils, who, incidentally, went pro the year before Mensik was born.

—Coco Gauff is one of Time magazine’s women of the year.

—Ivo Karlovic has officially retired.

—Jon Wertheim profiles Novak Djokovic, whom he declares the best ever.

—James Blake has been sanctioned for a gambling endorsement, and he’s not the first.

—Oh, dear. Tennis officials have “strongly recommended” players don’t leave the tournament grounds during the Mexican Open.

—A trailer for “Challengers” has been released.

—Giri Nathan moves out.