LONDON -- Novak Djokovic has equaled John McEnroe's number of matches won at Wimbledon by beating American Tennys Sandgren in straight sets.
Djokovic won 6-3, 6-1, 6-2 on No. 1 Court for his 59th match victory at the All England Club. That puts him level with McEnroe in fifth place on the all-time list, behind only Roger Federer, Jimmy Connors, Boris Becker and Pete Sampras.
Djokovic is looking for his fourth Wimbledon title, while Sandgren -- who reached the Australian Open quarterfinals -- was making his debut in the tournament.
Two-time champion Rafael Nadal moved into the second round with a 6-3, 6-3, 6-2 win over Dudi Sela of Israel.
The second-seeded Nadal hadn't played a match since claiming his 11th French Open title last month but showed little sign of rust as he cruised to victory against Sela.
Nadal is seeking a first Wimbledon title since 2010, which would also make him just the second man to accomplish the French Open-Wimbledon double three times.
He will next face Vasek Pospisil of Canada or Mikhail Kukushkin of Kazakhstan.
Nick Kyrgios served his way into the second round at Wimbledon, as the 15th-seeded Australian fired 42 aces and saved all five break points he faced to beat Denis Istomin of Uzbekistan 7-6 (3), 7-6 (4), 6-7 (5), 6-3.
Kyrgios earned the only break of the match to go up 5-3 in the fourth set before serving out the match. He reached the quarterfinals in his Wimbledon debut in 2014 but had to retire with a hip injury in the first round last year.
Fourth-seeded Alexander Zverev of Germany also advanced, beating James Duckworth of Australia 7-5, 6-2, 6-0.
Fifth-seeded Juan Martin del Potro maintained his record of never losing in the first round at Wimbledon with a 6-3, 6-4, 6-3 win over Peter Gojowczyk of Germany.
The Argentine will next face Feliciano Lopez, who broke Federer's record by appearing in a 66th consecutive Grand Slam singles tournament as he defeated Federico Delbonis of Argentina 6-3, 6-4, 6-2.
Matthew Ebden upset 10th-seeded David Goffin of Belgium 6-4, 6-3, 6-4 in just 1 hour, 33 minutes to earn his first win over a top-10-ranked player at a Grand Slam. The 51st-ranked Australian, who had lost all three previous meetings vs. Goffin, has never been past the second round at a major.
Dominic Thiem, the French Open runner-up, became the third top-10 player to exit the men's draw in the opening round when he retired hurt with his opponent, Marcos Baghdatis, leading 6-4, 7-5, 2-0.
Thiem, 24, received a medical timeout for treatment on his back before the pain eventually became too much early in the third set.
Baghdatis is into the second round for the ninth time in his career and will next face Spain's David Ferrer or Russian Karen Khachanov.
American Jack Sock, the tournament's 18-seed, continued his recent downward spiral, wasting a two-set lead and losing to 81st-ranked Matteo Berrettini of Italy 6-7 (5), 6-7 (3), 6-4, 7-5, 6-2.
Sock now has lost four consecutive first-round Grand Slam matches and five of his past six. He's also lost six matches in a row overall, dropping to 5-13 this season.
Sock reached a career-high No. 8 in the rankings in November and qualified for the season-ending 2017 ATP finals.
Kei Nishikori is into the second round after beating American qualifier Christian Harrison 6-2, 4-6, 7-6 (3), 6-2.
The 24th-seeded Nishikori saw off Harrison's attempt at a comeback by claiming a tight third set before cruising to victory in the fourth.
Nishikori, the top-ranked Japanese player at the tournament, will next face another Australian, Bernard Tomic, who made the first-round draw as a lucky loser and took full advantage by defeating Hubert Hurkacz of Poland 6-4, 6-2, 7-6 (2).
American Frances Tiafoe saved 13 of the 15 break points he faced to upset 30th-seeded Fernando Verdasco in the first round of Wimbledon. The 20-year-old Tiafoe relied on a strong serve to win 7-6 (6), 7-6 (5), 3-6, 6-3 over the Spanish veteran and reach the second round for the second straight year.
Tiafoe had only four break points himself but converted two of them as he repeatedly got the better of Verdasco on the big points.
"I played to win when it was time to step up," Tiafoe said.
The Associated Press contributed to this report.