There was a win over Andy Roddick at the 2009 U.S. Open, but casual fans may know Isner best for a marathon win over Nicolas Mahut at Wimbledon in 2010. They played the longest ever pro match, stretching 11 hours and 5 minutes over three days.
"I've just kept on surprising myself after each year. When I reached the top 50 in the world, that's actually when I actually did believe I could crack the top 10," he said. "I've always been a late bloomer."
Djokovic, the defending champion, fell to 14-2 this season, having lost to Andy Murray in Dubai earlier this month.
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