Li Na hits a forehand against Madison Keys (not pictured) on day seven of the Sony Open at Crandon Tennis Center in Miami, March 23, 2014. [Photo/Agencies]

KEY BISCAYNE, Florida - Li Na overcame three set points Sunday to rally past American Madison Keys 7-6 (3), 6-3 and reach the fourth round at the Sony Open.

The No 2-seeded Li, the reigning Australian Open champion, won despite struggling with her second serve. She had seven double-faults and was broken four times.

Keys failed to convert her set points serving at 5-3 in the first set. She also squandered a lead in the second set, when three times she was within a point of going up 3-love.

American CoCo Vandeweghe earned a shot at Serena Williams in the fourth round by winning a match that ended at 2:29 am. Vandeweghe, a qualifier ranked No 104, rallied past 2011 US Open champion Samantha Stosur 5-7, 7-5, 7-5.