Humbert, who was making his Wimbledon debut, advanced 6-7 (8), 3-6, 6-4, 7-5, 3-0. In the women's draw, former No. 1 Caroline Wozniacki advanced when her opponent had to retire in the first set. Wozniacki trailed 4-0 against Sara Sorribes Tormo but then won five straight games before the Spaniard retired.
In a matchup of youth vs. experience, the youngest woman in the draw beat the oldest at Wimbledon.
Fifteen-year-old Coco Gauff beat five-time champion Venus Williams 6-4, 6-4 in a first-round meeting between two players with a 24-year age gap on Court 1.
The 39-year-old Williams had won four of her seven Grand Slam titles before Gauff was even born in 2004.
The 313th-ranked Gauff is the youngest player to enter the main draw at Wimbledon since Laura Robson in 2009, having come through qualifying last week.
Gauff, playing in her first Grand Slam match, converted her fourth match point when Williams sent a forehand into the net, then broke into sobs before shaking hands with her opponent.
Novak Djokovic played a small part in Goran Ivanisevic's surprising Wimbledon victory in 2001, and he's hoping the retired Croat returns the favor this year.
Ivanisevic, who in 2001 became the first wild-card entry to win a Grand Slam title when he won Wimbledon, was sitting in Djokovic's box at the All England Club on Monday as the top-seeded Serb advanced to the second round.
"Didn't he tell you that was essential for his win here in Wimbledon, me bringing him the snacks?" Djokovic said with a laugh after beating Philipp Kohlschreiber 6-3, 7-5, 6-3.
"Actually, that's what happened. He was in Niki Pilic Tennis Academy in Germany, where I have spent quite a lot of time between age of 12 and 16. It happened to be that famous 2001 when he received the wild card here in Wimbledon, and he came over to the academy for several weeks. I had the permission to approach him while he was training and to bring him some snacks because he was hungry, training a lot."
Fast forward to 2019 and it's Djokovic and coach Marian Vadja that are hoping for some support to make yet another Wimbledon title run.
"We both agreed that we were looking for someone that was a former champion, someone that knows how I feel on the court, someone that has been through that," said Djokovic, a four-time Wimbledon champion. "We agreed with the concept, so to say, the idea of introducing a new coach to our team, an addition like Boris Becker was back few years ago. It was a very successful period with Boris. We're hoping we can have the same with Goran."
Sixth-seeded Alexander Zverev and seventh-seeded Stefanos Tsitsipas were both eliminated in the first round at Wimbledon.
Zverev lost to Jiri Vesely of the Czech Republic 4-6, 6-3, 6-2, 7-5, while Tsitsipas was beaten by Thomas Fabbiano of Italy 6-4, 3-6, 6-4, 6-7 (8), 6-3.
Both players are among the younger generation expected to eventually replace the Big Three of Roger Federer, Rafael Nadal and Novak Djokovic in men's tennis.
Tsitsipas, who beat Federer at the Australian Open en route to the semifinals, saved two match points in the fourth-set tiebreaker and failed to convert three break points early in the fifth. Fabbiano broke Tsitsipas twice in the final set, including in the last game when the Greek popped a shot long.
It was Fabbiano's first win over a top-10 player.
Naomi Osaka became the first top player to lose at Wimbledon, falling to Yulia Putinseva 7-6 (4), 6-2 in the first round.
The second-seeded Osaka, who won the U.S. Open last year and the Australian Open this year, was ranked No. 1 in the world until last week.
Osaka had 38 unforced errors on Centre Court, while Putinseva had only seven.
It was Osaka's second loss to Putinseva on grass this season. The Japanese player lost to the 24-year-old Kazakh in Birmingham two weeks ago.
Osaka lost in the third round at French Open.
French Open finalist Marketa Vondrousova has been knocked out in the first round at Wimbledon, losing 6-4, 6-4 to Madison Brengle of the United States.
The 16th-seeded Brengle broke Vondrousova seven times, taking advantage of 30 unforced errors from the Czech player.
Vondrousova reached her first Grand Slam final at Roland Garros, losing in straight sets to Ash Barty. She reached the semifinals at this year's Australian Open.
Vondrousova also lost in Wimbledon's first round in 2017 and 2018.
After an early wobble, defending champion Novak Djokovic got right back on track on Centre Court at Wimbledon.
Djokovic was broken in the opening game but recovered right away to beat Philipp Kohlschreiber 6-3, 7-5, 6-3 and reach the second round.
Djokovic, who is looking for his fifth Wimbledon title, lost to Kohlschreiber at Indian Wells this year but never looked in serious danger after that opening game, breaking his opponent five times.
Djokovic was playing with former Wimbledon champion Goran Ivanisevic looking on from his player's box, having added the Croatian to his coaching staff for the tournament.
Last year's runner-up Kevin Anderson reached the second round of Wimbledon by beating Pierre-Hugues Herbert 6-3, 6-4, 6-2.
Anderson hit 16 aces and saved all seven break points he faced.
The South African is looking for his first Grand Slam title after losing last year's final to Novak Djokovic, having beaten John Isner in a 6 1/2-hour five-setter in the semifinals.
Also in early action, three-time Grand Slam champion Stan Wawrinka advanced with a 6-3, 6-2, 6-2 win over qualifier Ruben Bemelmans of Belgium.
Wawrinka has won the French Open, U.S. Open and Australian Open but has never been past the quarterfinals at Wimbledon.
Play has started on Day 1 at Wimbledon in cool, dry conditions.
Among the players in early action on the outside courts are 2018 runner-up Kevin Anderson and three-time major champion Stan Wawrinka.
The high temperature is expected to be about 21 degrees C (70 degrees F) with only occasional clouds.
Matches on Centre Court and No. 1 Court are scheduled to begin later.
Novak Djokovic gets the honor of opening play on Centre Court at Wimbledon as the defending men's champion.
Monday's marquee matchup is scheduled for later in the day across the way at No. 1 Court: 39-year-old Venus Williams against 15-year-old Coco Gauff.
Williams is the oldest player in the women's field. Not only is Gauff the youngest, but the American is also the youngest player in the professional era to reach the main draw at the All England Club by going through qualifying rounds.
Williams had won four of her seven Grand Slam titles by the time Gauff was born.
Gauff considers Williams and her younger sister, Serena, her idols.
Other major champions in Day 1 action include Naomi Osaka and Stan Wawrinka.
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