PARIS, France -- American teenager Coco Gauff notched the biggest upset of opening-day play at Roland Garros, knocking out No.9 seed and 2019 semifinalist Johanna Konta of Great Britain, 6-3, 6-3.

16-year-old Gauff, who was making her Roland Garros main-draw debut on Sunday, claimed the fourth Top 20 win of her career as she eased past World No.13 Konta after an hour and 41 minutes of play on a chilly and damp day in Paris.

"I don't really take anything for granted, because I'm just happy to be playing," Gauff said, in her post-match press conference. "I don't think maybe winning matches at slams is something I'm used to, especially this is my first main draw at Roland Garros. When I'm on the court, I can act like I'm used to it. When I'm off the court, I'm just happy to be here."

Read more: Roland Garros Draw Analysis: Adaptability key to Paris title run

Gauff fell to Kaja Juvan in the qualifying rounds last year, but she has experienced recent success in Paris, winning the junior singles title as a 14-year-old over friend and doubles partner Caty McNally in 2018.

51st-ranked Gauff called Paris her "favorite city in the world" on social media. "I think it's just the culture and the architecture, the food, everything, I just really love it," said the American. "It's just so different from home. Especially the croissants, that's a personal favorite of mine. I haven't had any crepes yet. I have to stay healthy for the tournament. When it's over, I'll be eating a lot of those."

The youngest of the 11 teenagers in the draw, Gauff was sturdier on break points, converting five of 12, while Konta could only get two of seven over the line. Konta outwinnered Gauff by 22 to 14, but the Brit was wholly undone by 41 unforced errors on the day.

"I know that [Konta] likes to play really hard and play the ball into her," said Gauff. "So coming into the match I already knew I was going to change the pace and everything. To be honest, I was surprised how good the slice was today.

"I mean, the backhand slice I work on a lot. It's not the best, but I try to work on it. The forehand slice, I think it was just natural. I knew I had to change up the pace of the ball, especially in the conditions."

Gauff will now face Italian qualifier Martina Trevisan in the second round. Trevisan advanced past her countrywoman Camila Giorgi earlier on Sunday, after Giorgi retired from their all-Italian clash while trailing 7-5, 3-0.

A wide forehand miscue by Konta in the second game of the match gave Gauff an early break, and the Brit would spend the remainder of the set trying to recoup that loss, to no avail. Gauff stared down a break point in the very next game, but a missed return by the Brit let the teenager off the hook, and Gauff held on for 3-0.

Incredible clutch serving by Gauff erased two more break points in her next service game, as she gritted her way to a commanding 4-1 lead. The American at last had a breezy game on her serve in the next go-around, as she held comfortably for 5-2.

With Gauff serving for the set at 5-3, more strong first serves gave her five set points, but those all went begging after errors by the American, including five double faults in the game overall. But Konta, again, was unable to convert two additional break points in the game, and after the seventh deuce of the game, Konta misfired on two straight returns, giving Gauff the one-set lead.

After going 0-for-5 on break points in the first set (while the American was 1-for-1), Konta finally took advantage of a shaky service game by Gauff, breaking for a 2-0 lead in the second set. But the Brit double faulted at 30-30 in the following game to give Gauff a chance to break right back, and the American grabbed it, forcing a netted error with a fierce forehand to pull back on serve.

Konta used all of her court craft, including a clutch of divine dropshots, to extend her service game at 2-2 as far as she could, saving four break points in that game alone. But Gauff garnered a fifth break point, and on that opportunity, the 16-year-old chased down a dropshot and replied with a backhand winner to go up a break at 3-2.

Another break followed, which put Gauff up 5-2, before the youngster atypically faltered on serve, with two double faults in the game giving Konta two break points. A winning volley by the ninth seed gave Konta one break back as she continued fight to prolong the match, with a persistent drizzle beginning to cover the court.

Gauff, though, would remain unfazed, and in the next game, a deft dropshot led to a volley winner for the American, giving her double match point. Konta countered with a drop volley winner of her own to save the first, but on the second, a strong forehand by Gauff forced a netted backhand from Konta, and the teenage sensation moved into the Roland Garros second round for the first time.

2020 Roland Garros Highlights: Gauff conquers Konta in main-draw debut