John Isner rallies to beat Colombian qualifier in first round of Shanghai Masters

Santiago Giraldo of Colombia returns the ball against John Isner of the United States at the first round of the Shanghai Masters tennis tournament at Qizhong Forest Sports City Tennis Center, in Shanghai, China, Monday, Oct. 7, 2013. Isner won 4-6, 7-5 7-5. (AP Photo/Eugene Hoshiko) (The Associated Press)

United States' John Isner returns a shot from Colombia's Santiago Giraldo during the first round at the Shanghai Masters Tennis tournament in the Qi Zhong Tennis Center in Shanghai, China on Monday, Oct. 7, 2013. Isner won 4-6, 7-5, 7-5. (AP Photo/Ng Han Guan) (The Associated Press)

John Isner rallied to beat Colombian qualifier Santiago Giraldo 4-6, 7-5, 7-5 on Monday in the first round of the Shanghai Masters.

The 14th-seeded American fought off three break points at 5-5 in the third set, then broke Giraldo for the second time to close out the match.

Isner could meet Rafael Nadal in the third round.

Nadal, seeded second in Shanghai, supplanted Novak Djokovic as the top-ranked player on Monday, despite losing to the Serb in the final of the China Open in Beijing a day earlier.

Djokovic is the defending champion and seeded No. 1 in Shanghai. He could meet Roger Federer in the quarterfinals.

Djokovic, Nadal and Federer all have first-round byes.