He was the runner-up at the 2011 PTT Thailand Open, losing to Andy Murray, and had an illustrious junior career.
He won the Orange Bowl under-16 title in 2003.
He won the 2007 Wimbledon junior singles title.
His mother Illona and father Donald, Sr. are both tennis instructors and taught him to play when he was 3 years old.
He won the Australian Open junior title in 2005, making him the first American to win the tournament since Andy Roddick did it in 2000.