Jack Sock is an American tennis player. He won the 2011 US Open mixed doubles title with fellow American Melanie Oudin and the boys' junior US Open championship in 2010. Sock played his first ITF junior tournament in October 2008, aged 16, at the Pan American Championships. Sock began playing in Futures tournaments in 2009, winning his first senior tournament on that circuit in November 2011. His first match as a professional came at the 2010 US Open, where he lost to Marco Chiudinelli. In 2011, he achieved his best result to date in a Futures tournament, reaching the final of the USA F3 tournament. In 2011, he achieved his best result to date in a Futures tournament, reaching the final of the USA F3 tournament. After winning his first Grand Slam title, Sock returned to competing on the Challenger Tour. His most successful tournament was the Sacramento Challenger, in which he reached in the quarterfinals of the singles tournament and, partnering Nicholas Monroe, the final of the doubles tournament. In 2012, Sock won the Futures tournament at Plantation. In the final two months of the 2012 season Sock reached his first two Challenger Tour finals, winning at Tiburon in October and finishing as runner-up in the November Champaign-Urbana Challenger.