"Definitely a little relief," the sixth-seeded Williams said. "I was letting out a lot of cries. I was happy to get through that. . . . But as Kelly Clarkson says, 'What doesn't kill you makes you stronger.' "
Some other top players were sluggish at the start against unheralded foes on a day when action was cut short in the evening because of rain.
Two-time Wimbledon champion Rafael Nadal trailed, 4-0, against 80th-ranked Thomas Bellucci of Brazil before winning, 7-6 (0), 6-2, 6-3.
Defending women's champion Petra Kvitova fell behind, 3-0, and, 4-1, but eventually used a seven-game run to take control and beat 96th-ranked Akgul Amanmuradova, 6-4, 6-4. The match was halted by a 30-minute rain delay in the second set and when they returned, Kvitova needed all of three minutes to wrap it up.
Twelve singles matches were suspended in progress and four were postponed altogether. Among those that began but didn't finish, 2003 U.S. Open champion and three-time Wimbledon runner-up Andy Roddick led British wild-card entry Jamie Baker by a set and a break; French Open finalist Sara Errani was a point from beating U.S. qualifier CoCo Vandeweghe; and 21st-seeded Milos Raonic of Canada was a game from eliminating Santiago Giraldo of Colombia, leading by two sets and, 5-4, in the third.
Winners included 10th-seeded Mardy Fish of the United States, playing his first match since having a medical procedure on his heart a month ago. The 30-year-old Fish hit 24 aces and defeated Ruben Ramirez-Hidalgo of Spain, 7-6 (3), 7-5, 7-6 (1), then didn't attend a postmatch news conference - a tour spokesman said Fish wasn't feeling well, but didn't elaborate.
All three Australian men in action exited, meaning none reached the second round at the All England Club for the first time since 1938. No. 20 Bernard Tomic was knocked out by Belgian wild-card David Goffin; 2002 Wimbledon champion Lleyton Hewitt lost to No. 5 Jo-Wilfried Tsonga; and Matthew Ebden was beaten by Benoit Paire of France.