KEY BISCAYNE, Fla. -- Between points, Serena Williams stood motionless behind the baseline with her back to the net, as if trying to match -- or mimic -- the methodical ritual of her opponent, Maria Sharapova.
They took turns waiting on each other, the pace of play plodding, but there was no delaying the inevitable. Williams beat Sharapova for the 15th consecutive time Thursday, rallying in both sets to win 6-4, 6-3 in the Sony Open semifinals.
"I have always felt when I'm playing at my best, then it's hard for people to beat me," Williams said.
Seeking a record seventh Key Biscayne title, Williams improved to 16-2 against her favorite foil. Sharapova hasn't beaten Williams since 2004.
"Despite my results against her, I still look forward to playing against her because you learn so much from that type of level which she produces," Sharapova said. "You finish the match, and you know where you need to improve and the things that you need to work on."
The No. 1-ranked Williams won with a superior serve and better returns. She hit nine aces and broke five times, which helped her rebound from deficits of 4-1 in the first set and 2-0 in the second.
"I wasn't playing my best," Williams said. "I knew if I wanted to stay in the tournament and make another final, I just had to play better."
Li improved to 7-0 against Cibulkova. She won despite being broken seven times and committing 40 unforced errors, closing out the victory at 12:33 a.m. ET when Cibulkova hit a final forehand wide.
The No. 2-ranked Li is only 1-10 against Williams, but she leads the women's tour this year with a record of 21-2, including the Australian Open title in January.
Williams said she wouldn't scout the match.
"I never really watch," she said. "I get too nervous."
Williams first won Key Biscayne in 2002 and is the defending champion. A minority owner in the Miami Dolphins, she has worn the team's orange and turquoise throughout the tournament she considers her home event because she lives 90 minutes up Interstate 95.
"When I grew up I always wanted to play here," she said. "I guess I just don't want to let go. It's my favorite stop on the tour. It's home. All my friends come. So it's perfect for me."
There was no evidence of a home-court advantage at the start, when Williams failed to convert four early break-point chances and fell behind. Sharapova cracked a succession of winners from the baseline and earned applause from Williams after besting her in one exchange.
While Sharapova is notorious for her deliberate routine between points, Williams doesn't usually play so slowly.
"I just made some errors, and when that happened, I was just trying to regroup and get my mind back together and just try to get back focused and just try to get things going again," she said. "It just helps me to be able to relax. Sometimes I do get a little uptight."
The approach worked. Williams broke back when Sharapova committed three consecutive backhand errors, and gained momentum from there, sweeping the final five games of the first set.
The story was similar in the second set, and after falling behind, Williams resorted to her dominating power. She quickly won one game with two aces and two service winners during a stretch when she swept 11 consecutive points.
"In key moments she served really well today," Sharapova said. "Big serves. I got a few of them, but not good enough to get myself back in the point."
Williams' rhythm and pace improved as the match progressed. She peaked at 122 mph.
"I hadn't been serving great too much this tournament, and then I started serving a lot better today," she said. "I was hitting 120. I was like, 'Whoa. Is that me?' "
Sharapova committed groundstroke errors on the final three points, and a victorious Williams trotted to the net, her left fist leading the way.