Answer
Marat Safin, a two-time Grand Slam champion, fell to Jesse Levine in the first round of Wimbledon in 2009. Levine, then ranked 117th in the world, upset the 19th-seeded Safin in four sets, 6-2, 3-6, 7-6(6), 6-4. It was a significant victory for Levine, who had never before defeated a top-20 player.