"I haven’t completed a match since July, so I think it’s always challenging to come back from not one injury, but a few," Sharapova said. "I was just really thrilled that despite not playing these last few months and not playing my best tennis, I was able to take myself to another level physically, which I didn’t exactly expect that I would be able to."
Third-seeded Sharapova, looking rusty from the lack of match play, needed 2 hours, 47 minutes to finally nail down the win against fifth-seeded Radwanska.
The Russian’s serve was erratic and while she posted eight aces, she also double-faulted 12 times.
Sharapova served for the match at 5-2 but dropped her serve. At 5-4, she double-faulted on her first match point, but won the match two points later when Radwanska netted a forehand.
"Matches like this, I think they take a few years out of your life," Sharapova said. "But you know what? I’m happy I got through it. Yeah, I’m going to feel it tomorrow. I’m proud that I was able to get through."
In the first set, Sharapova netted a backhand on a second break point in the ninth game to hand Radwanska the service break.
Radwanska served out the first set in the next game off another Sharapova backhand error.
Sharapova raced to a 4-1 lead in the second set. Although she surrendered one of her two service breaks in the seventh game, she prevailed to send the match into the decisive third set.
This marked Sharapova’s 13th career win in 15 matches played against Radwanska. It was also the third time they played a marathon encounter at the season-ending tournament.
In 2012 and 2014, Sharapova also defeated Radwanska in three-set, three hour-plus round-robin matches at the WTA Finals.
"I think we (are) always playing three hours match in championships, so I’m not surprised," said Radwanska, a two-time semifinalist at the WTA Finals. "I guess she was just better today."
Sharapova won the WTA Finals in her debut at the tournament in 2004. She was also a finalist in 2007 and 2012.