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It takes a lot to win a share of crowd loyalty in Arthur Ashe Stadium in New York City in the year of the resurrection of Roger Federer. It takes so much that it did not appear remotely possible for anyone not named Rafael Nadal. But last night at the U.S. Open, over five improbable sets, someone earned it, and it was someone who couldn’t have been more deserving: Maryland-born, 19-year-old Frances Tiafoe, son of a custodian at the tennis facility, wielding idiosyncratic strokes of his own devising. Even as Tiafoe went down 4-6, 6-2, 6-1, 1-6, 6-4, he gave Americans the perfect little kernel of hope to begin the Open, and look to the decade ahead.

That the teen played well last night was not an absolute surprise. Tiafoe gave Federer a little fright this year in Miami, and the Swiss can be slow to start as he feels out an opponent, hunting for cracks in the veneer. Tiafoe revealed almost none. He broke serve immediately and then kept up the pressure with his spinny, heavy groundstrokes and flat-out foot speed, a combination that has worked nicely for a certain Federer-beater in the past. Stir in the fact Federer was playing his gawkiest tennis of the year, moving a bit like what he is—a 36-year-old dad struggling with some back issues, seemingly in need of a good foam roll or deep-tissue massage—and the result starts to make sense. Just look how well Frances was striking his tentacular forehand:

But things settled back down to reality in the next two sets. Tiafoe can crack a blistering ball from the back of the court, but like many young players he looks infinitely less confident when moving forward. In the second set he had his fair share of net mishaps, whether due to overcooked approach shots (for lack of confidence in his volleys, perhaps) or hesitant footwork:

Watching him play, Tiafoe’s unusual groundstrokes might be what most immediately cry out for coaching—mostly his shank factory of a forehand, with its severe grip and gaudy loop—but then you have to wonder how difficult it would be to radically rethink a stroke that he’s grooved into his muscle memory for so long. (Ernests Gulbis did this several times over, but, for all his wild latent talent, Ernests Gulbis is not exactly one to model a career after.) Maybe Tiafoe could tidy up his preparation on his forehand, but the most immediate area of improvement could simply be his shot selection and net touch. He’s going to earn a lot of short balls because he can really pound the ball, and he’s going to get to those balls easily because he’s fast as hell, so he has got to learn what to do with them. The American was nine of 17 from the net on the match. Get thee to a doubles court, Frances.

In the third set Roger got hot and served him a 6-1 breadstick, and the match began to resemble just another early-round straight-set rout with a fluky first set as appetizer. But then something changed. I’d be lying if I said I knew exactly how the fourth set went down; by then my attention had drifted to the latter parts of my dinner. But when I looked back, Federer was faltering, Tiafoe was playing out of his teen mind, breaking serve twice and handing Federer a 6-1 set of his own.

The deciding set brought forth some of Tiafoe’s best stuff. By then, he could clearly hold his own in the neutral rallies. While his forehand is the scene-stealer, his compact two-hander does a lot of the heavy lifting.

Backed into a corner with Federer serving for the match and yet still off-kilter, the shots presented themselves to Tiafoe, and he made the damn shots:

On the very next game, however, he failed to hold serve, so Federer survives at least one more night. It was a sloppy match all around: Federer sprayed 56 errors to his 41 winners; Tiafoe had 49 and 23 respectively. Federer’s first-serve percentage on the match was a bleak 54 percent, well down from the 63 percent he’s been averaging over the last year. To be clear: His tournament will hinge on the state of his back. As much as the city worships him, and as much as the U.S. Open desperately needs him to linger into the late rounds of a star-sapped draw, there is no eliding the fact that Roger Federer does not look all that healthy. He may not be tested much for the next few rounds—he has 35-year-old, No. 101 Mikhail Youzhny in the next match—but even a raw Tiafoe, with only two career wins over top 70 players, seemed like test enough.

Tiafoe, for his part, will hopefully be more than just another nameless casualty on Federer’s unsteady march through this soft field. Unlike a much surer bet like Alexander Zverev, it’s hard to envision exactly what Tiafoe will become, but the potential is there, and after last night’s show under the lights, he now has a nation’s full attention.