Mardy Fish of America overcame two set deficit to defeat former World No. 3 and two-time US Open semi-finalist Nikolay Davydenko 4-6, 6-7(4), 6-2, 6-1, 6-2 in the second round encounter of the US Open 2012 Tennis Championships.

Fish struggled to keep the ball in play in the first set and lost it on a tame note. The American displayed better play in the second set and took the set to a tie breaker, where he made five unforced errors to gift Davydenko a two-set lead in the match.

Things changed dramatically after that as Fish broke the Russian seven times over the final three sets to register the victory in 3 hours and 26 minutes.

Fish will next take on the winner between Frenchman Gilles Simon and qualifier Jimmy Wang.

In a huge upset of the day, Martin Klizan of the Slovak Republic ousted fifth seeded Jo-Wilfred Tsonga of France 6-4, 1-6, 6-1, 6-3.

"I was coming to the match to play a very solid game," said Klizan. "I wanted to play really good tennis to play with the top star player. I played very, very well today. I was concentrating each point and I won; I'm very happy that I did.