Un, Deux, Trois: Three takeaways from the first day at Roland Garros

Later, world No. 253-ranked Nicolas Mahut justified his wild card with his biggest career win over 2018 semifinalist Marco Cecchinato, 2-6, 6-7 (6), 6-4, 6-2, 6-4. The Frenchman had not come back from two-sets-to-love down since the 2011 US Open.

The 37-year old crowd favorite enjoyed a standing ovation with his seven-year-old son, Natanel. Mahut is ranked No. 5 in doubles, and is the defending champion—though not with his usual partner Pierre-Hugues Herbert.

It was a great first day on Court Simonne-Mathieu, and all around the grounds. Expect a lot more there, and everywhere else, on Day 2.

Roland Garros 2019 commenced with a whirlwind of upsets, triumphs and one of the game's biggest returns. It was a very eventful first day, and it's safe to say the fortnight will definitely keep everyone on their toes. Here are the three biggest takeaways from opening day.

The 20-time Grand Slam champion arrived to a standing ovation as he entered the newly updated Philippe Chatrier Court and left the excited crowd on their feet as he comfortably defeated Lorenzo Sonego, 6-2, 6-4, 6-4, in just one hour and 41 minutes. He moved and executed his shots with grace and resembled much of the same player who took the title in 2009. Sunday marked his first match back on the Parisian clay courts since 2015.

"I'm very happy to be back," he said. "Maybe a tiny bit more because when I have missed the last three editions, and when you miss something in life, you're happy to be back there again."

Federer shook off any concerns over the leg injury which forced him to withdraw from last week's Italian Open. The Swiss will continue his run on Wednesday against qualifier Oscar Otte.

The gloomy weather over Philippe Chatrier translated over into a dismal outcome for Angelique Kerber, as 18-year-old Anastasia Potapova powered past the No. 5 seed, 6-4, 6-2, in 73 minutes. This is only Potapova's second clay-court main-draw win of 2019, outside of Fed Cup play. Potapova's win ended Kerber's hopes of a career Grand Slam, at least for this year.

“My phone is exploding now,” Potapova said. “I really appreciate it. It's nice to hear congratulations from great people."

The teen seemed to play with no nerves, drilling balls from side-to-side and forcing Kerber to run and eventually leave balls short. The blistering intensity of Potapova's hitting proved to be too much for Kerber, as the Russian dominated in relentless fashion, punching holes into her opponent's weaknesses. Will she be the next Jelena Ostepenko—who captured the title on her 2017 debut? It may be a little too soon to tell.

Potapova continues her dream week against the winner of Wang Yafan and Marketa Vondrousova.

It's only day one at Roland Garros, but it's clear the tournament already has a big winner. The newly updated Simonne-Mathieu show court is beautiful, intimate and surrounded by four greenhouses. The court already offered fans exciting tennis in its debut.

Former champion Garbine Muguruza became the first winner on Simonne-Mathieu. Although Muguruza was rattled, losing the first set against Taylor Townsend, 7-5, she kept her composure to take the second and third sets, 6-2, 6-2. A ceremony to celebrate the court's opening was held following Muguruza's win.

"It's actually cool to be the first player [to win] in it," Muguruza said to the full crowd. "I have been training this week on it for a couple of days. I liked it. It's a very cute court. It's not small, but it's cozy."

Later, world No. 253-ranked Nicolas Mahut justified his wild card with his biggest career win over 2018 semifinalist Marco Cecchinato, 2-6, 6-7 (6), 6-4, 6-2, 6-4. The Frenchman had not come back from two-sets-to-love down since the 2011 US Open.

The 37-year old crowd favorite enjoyed a standing ovation with his seven-year-old son, Natanel. Mahut is ranked No. 5 in doubles, and is the defending champion—though not with his usual partner Pierre-Hugues Herbert.

It was a great first day on Court Simonne-Mathieu, and all around the grounds. Expect a lot more there, and everywhere else, on Day 2.