Serena Williams won a record seventh Key Biscayne title when she overcame a slow start to beat Li Na 7-5, 6-1 at Miami.
But on a muggy spring afternoon, the number one-ranked Williams looked sluggish at the outset and served poorly, and she was broken twice to fall behind 5-2.
I just was able to relax as whenever I relax, I enjoy myself.
"At that moment I felt like I had nothing to lose," Williams said.
"I just was able to relax as whenever I relax, I enjoy myself."
Li held a set point serving at 5-4, but Williams erased it with a backhand winner.
Williams needed another 21 minutes to pull out the set.
The final game of the set went to deuce six times, but she finally won it with a booming backhand that Li couldn't handle.
She dominated from there, sweeping the final five games, and closed out the victory with a service winner.
It's a commentary on the yawning gap between Williams and the rest of the women's tour that she won in straight sets against the number two-ranked player while playing less than her best.
She made only 44 percent of her first serves and converted just five of 17 break-point chances.
Williams lives 90 minutes from Key Biscayne and considers it her home event. She said the fans provided a boost when she fell behind.
Williams surpasses Agassi
Williams surpassed the tournament record of six titles she shared with Andre Agassi.
Li, who won the Australian Open in January, was at the top of her game for most of the first set, but still could not close it out.
"Only one mistake: I think I should go party last night," Li said with a smile.
The world's top-ranked players will also meet in the men's final on Sunday, when Rafael Nadal tries for his first Key Biscayne title against Novak Djokovic, a three-time champion.