Sixth seed Roger Federer survived a massive scare against Adrian Mannarino before advancing to the Wimbledon second when the Frenchman retired with a knee injury after slipping on court.
The match was poised at 6-4 6-7(3) 3-6 6-2 with the eight-times Wimbledon champion forcing a fifth set before Mannarino, who was celebrating his 33rd birthday, decided he could not continue.
Federer was serving with a 4-2 lead in the fourth set when the 41st-ranked Mannarino slipped while attempting a return and twisted his right knee.
The Frenchman received medical attention on Centre Court and limped back to complete the set before shaking hands with Federer, who now has a 7-0 head-to-head record against him.
Federer, at 39 the oldest man in the draw at this year's grasscourt Grand Slam, will meet either Frenchman Richard Gasquet or Yuichi Sugita of Japan for a place in the third round.
Medvedev eases into second round
A few days after claiming his first grasscourt title in blazing Mallorcan sunshine, second seed Daniil Medvedev could easily have been caught cold in his Wimbledon first-round match.
But on a chilly and damp evening at the All England Club he showed he is not just a fair weather player on the lawns to overcome German powerhouse Jan-Lennard Struff.
Medvedev's title run on the Mediterranean holiday island marked the Russian out as a serious Wimbledon challenger.
Struff was hardly the easiest of draws, having beaten Medvedev on grass in Halle this month, but the world No.2 avenged that loss with a 6-4 6-1 4-6 7-6 victory.
Meanwhile, fourth seed Alexander Zverev of Germany fired 35 winners and sent down 20 aces to ease past Dutch qualifier Tallon Griekspoor 6-3 6-4 6-1 in 89 minutes.
Briton Dan Evans snapped a four-match Grand Slam losing streak by beating Feliciano Lopez 7-6(4) 6-2 7-5.
American Sebastian Korda defeated Eastbourne champion Alex De Minaur 6-3 6-4 6-7(5) 7-6(5).
Earlier, 26th seed Fabio Fognini beat Albert Ramos-Vinolas 7-6(4) 6-2 6-4 in a match carried over from Tuesday.
