Serena Williams capped off a season to remember by capturing her fourth WTA Championship title with a 2-6, 6-3, 6-0 win over Li Na on Sunday.
The 32-year-old American finished off a dominant year, in which she also won the French and U.S. Opens, by scooping up her 11th title of 2013.
China's Li, who will reach a career-high third in the WTA rankings on Monday, broke Williams's serve twice in the first set.
However, the World No 1 shifted gears in the second set to roar through 6-3, to the delight of more than 16,000 fans who filled Istanbul's Sinan Erdem dome.
Williams showed little sign of the fatigue she complained about a day earlier, flattening Li in the third set with her brutal power and on court coverage.
The 17-times Grand Slam winner, who has played over 80 matches this season, said there was still room for improvement.
"I live to win slams. I really don't know if this was my best season ever, but definitely top 3. I still have things to add to my game," she said without elaborating.
The opening game of the second set, which featured nine deuces, was the turning point.
"Looking back the first game of the second set was definitely a very important game for me to win. Li had been on a real roll. I guess I was determined to win that game at any cost," she said.
Quizzed about the gap between her and the other players, Williams said: "I'm just playing, and I'm trying to do the best that I can. I don't know if there is a gap."
Mental strength is the key to Williams's dominance, according to Li's coach Carlos Rodriguez.
"As we saw today, the tennis gap between Serena and the rest of the players is not much. But mentally, she's over the top, and she's by far the greatest player at the moment," said Rodriguez, the man who shaped former world number one Justine Henin's career.
Li admitted nerves played a part in her defeat.
"I was too excited at the start of the game, and by the half of the second set, I had no more energy left," she said.
But the 31-year-old Chinese, who served 10 double faults, was not too concerned.
"I have showed much improvement this year, and this serve-volley thing is new to me, and it's not like playing from the baseline," she explained.
"I was feeling much better than the US Open. At least this time I tried to do my best," said Li, who won only three games when she lost to Williams at Flushing Meadows in September.
Image: Serena Williams of the U.S. celebrates her victory against Li Na of China in their WTA tennis championships final match at Sinan Erdem Dome in Istanbul on Sunday
Photograph: Murad Sezer/Reuters