Nothing to worry about.
Venus was correct -- barely. Serena hit a Wimbledon record 23 aces, held every service game and narrowly escaped an upset bid by Jie Zheng, winning 6-7 (5), 6-2, 9-7 in the third round Saturday.
Williams, who erased all six break points she faced, served three times to stay in the match and held each time at love. She was pushed to deuce serving in the final game but closed out the victory with a volley winner, then hopped in glee on the Centre Court grass.
"I just wanted to get through that match," Williams said. "The last thing I wanted to do was lose."
The 5-foot-4½ Zheng, seeded 25th, played with little flash but plenty of consistency, committing just 17 unforced errors. She hung in the match despite hitting only one ace.
Venus Williams -- a five-time champion who lost in the first round -- may not have been concerned, but Serena looked plenty worried. She rocketed a return to break for an 8-7 lead in the final set, then showed how much she wanted to win, throwing back her head and letting out a long scream.
Williams has been stalled at 13 Grand Slam titles since winning Wimbledon for the fourth time in 2010, and dealt with a series of health issues in 2010-11.
Her next opponent will be unseeded Yaroslava Shvedova of Kazakhstan, who won all 24 points in the first set -- a so-called "golden set" -- and beat French Open runner-up Sara Errani 6-0, 6-4. It's the first known golden set by a woman in the Open era, the International Tennis Federation said, and the BBC showed a highlight package of all 24 points.
Williams will face Shvedova on Monday.
"Hopefully I'll be able to win a point in the set," Williams said. "That will be my first goal, and then I'll go from there."
Azarenka reached the semifinals last year at the All England Club before losing to Kvitova. They are now two rounds away from a rematch in the semifinals.
Azarenka broke the 178th-ranked Jana Cepelova five times while losing her serve twice. She is looking for her second Grand Slam title after winning this year's Australian Open as part of a 26-match winning streak.
Cepelova was playing in her first Grand Slam tournament.
On a sunny, windy afternoon, the retractable Centre Court roof was open after being closed all day Friday, and the breeze that had Williams' skirt flapping might have contributed to her slow start. She struggled with her return, and several times shanked serves by Zheng that barely reached 100 mph.
Williams didn't have a break-point chance in the first set, and every point Zheng won in the tiebreaker came on an error by her opponent, including two mishit returns.
"I thought, 'Serena, just relax and be calm,'" Williams said. "I felt good. I never felt like I was going to lose this match."
Williams briefly locked on Zheng's serve in the second set, sweeping the final 13 points to even the match.
In the last set, Williams overcame a love-40 deficit to hold for 2-all. Two games later, when she bounced a kick second serve over her opponent's head for an ace, Zheng managed a laugh.
Later in the set Williams won 14 consecutive service points, including three aces in one game to reach 7-all. She held 18 times and lost only 18 of 98 service points.
"It's a tough match, because she has big serve," Zheng said. "It's very difficult against her on the grass court."
The 14th-seeded Ivanovic, whose only Grand Slam title came in Paris in 2008, came back from a set down to beat 22nd-seeded Julia Goerges 3-6, 6-3, 6-4. Kvitova had an easier time, beating unseeded Varvara Lepchenko of the United States 6-1, 6-0.
Schiavone, seeded 24th, played with her usual varied and attacking style to defeat 31st-ranked Klara Zakopalova 6-0, 6-4. Schiavone won the 2010 French Open, then was the runner-up last year. She reached the fourth round at Wimbledon for only the second time in 13 appearances.
Ivanovic's best showing at Wimbledon was a run to the semifinals in 2007. She lost in the third round last year and the first round in 2010.
Against Goerges, Ivanovic kept teetering on the edge of real trouble. Serving for the match, she faced a break point at 30-40, and came up with a cross-court forehand winner that clipped the outside edge of a line. An ace set up match point, and Goerges then netted a forehand.
Information from The Associated Press was used in this report.