KEY BISCAYNE, Fla. -- Serena Williams punctuated points Saturday with theatrics worthy of a Grand Slam final. There were squeals, knee kicks, pirouettes and fist pumps, sometimes all at once.
In other words, Williams appeared to be 100 percent.
Showing no lingering effects from a recent knee injury, the seven-time Key Biscayne champion won her opening match at the Miami Open on Saturday, beating Monica Niculescu 6-3, 6-1.
The match was the first for Williams since she withdrew before the semifinals at Indian Wells last week, citing a right knee problem. She played without a wrap on her knee and said it is feeling much better.
"It was a little sore in practice, but it was OK today," she said.
Despite the lopsided score, the match was not without tension. Williams also beat Niculescu two weeks ago but nonetheless struggled at the start with the Romanian's unorthodox game, which includes a squash-style slice forehand that creates lots of spin.
When flummoxed, Williams didn't try to hide her emotions.
"I'm clearly frustrated," she told the crowd afterward. "I just try not to explode, which is hard because I'm really passionate."
The top-seeded Williams began to dominate when she started moving toward the net, and she won nine of the final 10 games. She will face 15-year-old American CiCi Bellis in the third round Sunday.
Serena's sister Venus also advanced, beating Samantha Stosur 6-4, 7-6 (3). The older Williams' opponent in the fourth round will be No. 4 Caroline Wozniacki, who rallied to beat Kaia Kanepi 4-6, 6-1, 6-3.
Eugenie Bouchard was upset Saturday at the Miami Open by qualifier Tatjana Maria 6-0, 7-6 (4).
Bouchard, who was seeded No. 6, won less than half her service points, had five double-faults and was broken five times.
The Canadian, a Wimbledon finalist last year, has a 6-4 record this year. Her career record at Key Biscayne fell to 1-3.
"I'm going to take a day off," Bouchard said, "and then I'm going to practice a lot and try to put this one behind me as soon as possible."
Maria, a German ranked 113th, beat a top 10 player for the first time since 2010.
Serena Williams had a first-round bye, and she waited even longer to play because her opening match was postponed Friday night due to rain.
She eased any doubts about her knee by chasing down a lob midway through the first set. On the run with her back to the net, she scooped back an improbable shot and went on to win the point.
"I was surprised I was able to get it," Williams said. "I'm really fast when I want to be. I can get any ball I want to. My coach is always like, 'If you want it, you can do it.' I just have to want every ball. I guess I wanted to get to that."
The two-time defending champion won her 13th consecutive match on Key Biscayne and extended her winning streak on the tour this year to 16 matches.
No. 8 Ekaterina Makarova, No. 11 Sara Errani and No. 13 Angelique Kerber also moved into the third round.