NEW YORK -- Venus Williams had been 14-0 in the first round of the U.S. Open, though she never had to face an opponent ranked in the top 30 at that stage.
Williams was usually the seeded player, but after two years of illness and injury, the seven-time major champ was the one pulling the upset Monday when she defeated Wimbledon semifinalist Kirsten Flipkens.
Her ranking down to No. 60, Williams beat the 12th-seeded Flipkens 6-1, 6-2 for one of her biggest wins since she pulled out of this tournament two years ago because of Sjogren's syndrome, an autoimmune disease.
"For me, I stay positive because I know I can play great tennis," Williams said. "Sometimes you just have to go through more than what you want to go through. Sometimes you have to have losses. When I had losses, it always motivates me a lot to do better and to work harder."
The 33-year-old looked strong Monday, fighting off three break points at 2-2 in the second set in a game that went to six deuces.
"If Venus is there -- if she's fit, if she's focused -- she's a top-10 player," Flipkens said. "Everybody who knows a little bit of the game of tennis can see that. Today, she was like a top-10 player."
Bothered by a lower back injury, Williams was playing just her third event since a first-round loss at the French Open. She hadn't defeated a top-20 opponent since last October.
"I realize that I haven't had a lot of chances to play this year or a lot of chances to play healthy this year, have had injuries and what have you," she said. "So I'm just going to have to keep working my way into it maybe more than some of the other players. But I know I can do that."
Flipkens, meanwhile, had been enjoying a career year. The Belgian had never reached the round of 16 at a major tournament before the Australian Open, then made her run at Wimbledon.
Hours after Venus advanced, sister Serena was so dominant in her opener that her opponent really needed a hug.
So midway through the second set of defending champion Williams' 6-0, 6-1 victory, Francesca Schiavone wandered behind the baseline, found a ball boy and enveloped him in a full-fledged embrace.
It was that kind of evening for Schiavone, an often-demonstrative player who is certainly no pushover: She won the 2010 French Open, and was the runner-up at that Grand Slam tournament a year later. She's been ranked as high as No. 4 but is 54th this week.
"I knew playing a former Grand Slam champion in the first round was a really, really tough draw," Williams said, "so I tried to be super serious."
The No. 1-ranked Williams was nearly perfect, making only eight unforced errors, compared with a 13-3 edge in winners, hitting serves faster than 115 mph, and taking the first 10 games.
"It was tough today," said Schiavone, who is working with Peter Lundgren, one of Roger Federer's former coaches. "Really, really tough."
When Schiavone finally got on the board more than 50 minutes into the match, holding serve to win her first game with a volley winner, she swung her right fist in a celebratory roundhouse punch and shouted. Her face then broke into a wide smile while she strutted to the sideline, and she tossed her racket toward her changeover chair.
"It was very, very nice to win a game," Schiavone said. "For the first time in my life, I felt joy from winning a single game."
At Williams' news conference, she was asked by an Italian reporter: "Did you really want to win 6-love, 6-love against the poor Schiavone?"
That drew a chuckle from Williams, who responded: "No, it wasn't that. I was just out there, trying to be focused."
Stephens, seeded 15th, lost the first set to the 110th-ranked Minella and trailed 4-2 in the third, then 3-1 in the final-set tiebreaker.
Stephens won five straight points from there, then closed it out on her third match point to improve to 9-1 in the first rounds of majors.
Stephens heard plenty of support from the crowd, of course. She also picked out one particular voice in the stands that tried to remind her of at least one reason to be motivated.
"Someone yelled to me, 'If you don't get it together, this lady is going to take your second round prize money!' I was like, 'Oh, God,'" Stephens recounted.
This was the second time in three years Stephens needed a third-set tiebreaker to win her opening match at Flushing Meadows.
Stephens made her first career Grand Slam semifinal earlier this year at the Australian Open, then followed that by making the fourth round at the French Open and quarterfinals at Wimbledon.
With her recent showings, Stephens has only increased expectations -- particularly when competing on home turf.
"There's more eyes on me," said Stephens, who is based in Coral Springs, Fla. "Just the whole being here at the U.S. Open is a bit overwhelming. Literally everywhere you go, every single person knows who you are, as opposed to when you're at the French Open or when you're at Wimbledon."
In the tournament's first match at Arthur Ashe Stadium, Radwanska needed only 63 minutes to improve to 28-2 in Grand Slam openers. She won 15 of 21 points at the net.
Radwanska withdrew from her last tournament (Cincinnati) on Aug. 15 before her quarterfinal against Li Na to fly home for her grandfather's funeral.
"Sometimes there are some things more important than tennis," Radwanska said. "It was something like that, and it was really a pretty quick choice. Of course, this is the situation that we have to be home for the family, and I think I owed my granddad to be there."
The US Open is the only major tournament in which the Polish star has never made the quarterfinals. She has reached that stage at the first three Grand Slam events this year, something no other woman accomplished.
The 69th-ranked Soler Espinosa, from Spain, advanced to the third round at the US Open the past two years.
Fifth-seeded Li needed just 64 minutes to win her first-round match against Olga Govortsova.
Li didn't face a break point and had 28 winners, winning 6-2, 6-2.
The US Open has been the least successful Grand Slam event for the 2011 French Open champion, who has advanced past the fourth round only once.
The 88th-ranked Govortsova, from Belarus, reached the third round at the US Open last year.
Information from The Associated Press was used in this report.