text: (CNN) -- Marathon man John Isner survived another epic on his return to competitive tennis after his record-breaking 11-hour Wimbledon match. 
  
  The American saved two match points before beating Gilles Muller, from Luxembourg, 4-6 7-6 7-6 to seal his place in the quarterfinals of the Atlanta Tennis Championships. 
  
  It is Isner's first tournament since Wimbledon back in June when his opening round victory over Frenchman Nicolas Mahut in London clocked in as the longest match in tennis history. 
  
  Isner's battle with Mahut stretched over three days and 183 games before he finally triumphed, 6-4 3-6 6-7 7-6 70-68. He later told CNN: "I really didn't think it was going to end." 
  
  Isner reflects on 'crazy' Wimbledon match 
  
  The match turned Isner into a household name in the sport, and after his straight sets defeat to Thiemo de Bakker in the second round the 25-year-old targeted a prolonged period of rest. 
  
  But on his return to the court he was made to work hard by Muller, saving two match points and firing 33 aces as he won in two-and-a-half hours to delight the 5,000 strong crowd. 
  
  "I didn't want to let [the fans] down," Isner told the ATP tour website. "I didn't want to lose my first match here. Also, I had a lot of friends and family here, so I didn't want to go out early. 
  
  "I hadn't seen a live ball in quite some time and Gilles was never going to give me rhythm with his lefty serve. I felt I was shedding the rust off in the second and third sets. I will only keep getting better. 