PARIS — Frances Tiafoe’s face expressed what the scoreboard had not. Tiafoe, a 17-year-old from College Park, Maryland, lost his Grand Slam main draw debut Monday to 36th-ranked Martin Klizan, 6-2, 6-1, 6-4.

While able to hammer 11 aces, including eight in the third set, Tiafoe held only half of his service games and several times saw his second serves smacked back for clean winners by Klizan.

Despite the potentially humbling experience, Tiafoe remained upbeat through the more competitive third set, which he led, 3-0, after earning a break when Klizan double faulted.

In his news conference, Tiafoe’s answers were often clipped, interrupted by his own broad smiles pushing through.

“It was great; I had a blast,” he said. “I didn’t play my best today. He’s playing very well this year. I knew it was going to be a tough match. In the third set I started playing a little better and had some opportunities. The crowd was great. Hopefully I can play again in the main draw next year.”

Tiafoe had not expected to be in Paris this year and had scheduled several smaller tournaments in Mexico for this stretch of the calendar. He started this year ranked 1,136th and only turned professional in April. But his trajectory spiked upward once the season shifted to clay, and his performance at three consecutive Challenger-level events played on green clay in Florida and Georgia earned him a reciprocal wild card into the French Open.

Now ranked 287th, Tiafoe was quick to answer when asked what he learned from the match.

“I need to get a lot better,” he said with a laugh.

Roland Garros was not entirely new to Tiafoe: He had been the top seed in the junior draw last year, and he lost in the second round.

“A lot of people were looking up to me last year when I was the one-seed,” he said. “Now I’m looking up to everyone here. It was definitely a lot different. But, I mean, I’ve got to get used to it, I guess.”

The excitement for Tiafoe was visible. With seating limited to three rows on each side of Court 5, a long queue of fans formed waiting to see the match.

“It’s always nice,” Tiafoe said of the attention. “But you’ve got to also know where you stand and know there is a long way to go from where I really want to be. I never really let any of that get to me, because I know it still is a long way for me to get to the top.”

Klizan, who himself was a highly-touted teen prospect, was reserved in his assessment of Tiafoe’s potential.

“Everybody has a chance,” Klizan said. “If he uses the chance, if he works hard, then he can be good. I can’t say if he’s going to be top 10 or top 100. Nobody knows; it’s just all about him.”