World No. 52 Martin Klizan of Slovakia pulled off the biggest upset of the 2012 U.S. Open this afternoon when he shocked fifth-seeded Jo-Wilfried Tsonga 6-4, 1-6, 6-1, 6-3 in a second-round match. The 23-year-old Klizan had never made it past the second round in three Grand Slam appearances. In fact, he had never defeated a player ranked higher than No. 49. Klizan showed more firepower throughout the match than the big-hitting Frenchman. The 6-foot-3 Slovak had five aces to Tsonga’s four, and hit 32 winners to his opponent’s 28. “I had no pressure,” Klizan said. “If I lose, then I lose. I lose with (a) good player. But I won and I’m very happy. It means for me more that I beat finally a guy from the top 10.” Tsonga looked lethargic throughout much of the match, prompting many to wonder if he was going to call the trainer out to address some kind of issue. It never happened. “Today I was not in a good shape,” Tsonga said. “I didn’t play good tennis. It seemed like I couldn’t hit the ball hard enough to put my opponent out of position. I don’t know know why it was like this today, but sometimes it happens with me.” Klizan broke Tsonga in the first game, off a sloppy backhand error, one of many careless errors the Frenchman committed on the day. Tsonga broke back in the fourth game to even the set at 2-2, but was broken at love in the seventh game. Down a set, Tsonga raced out to a 5-0 lead in the second and closed it out 6-1 in just 28 minutes. Klizan won 10 of the next 11 games to take a 4-0 lead in the fourth. After getting broken in the sixth game, the Slovak found himself in a tense spot, serving at 4-3, deuce. But he steadied his nerves and held, and then broke Tsonga in the final game to seal the win in two hours and 12 minutes.