BASEL: Gilles Muller unleashed 17 aces as he stormed back for a 6-7 (9/11), 6-4, 6-4 victory over Grigor Dimitrov in the Swiss Indoors first round on Tuesday.
The 33-year-old veteran from Luxembourg lost the opening set but made the last two count as he fought through in just under 2.5 hours to earn the upset win.
Muller produced 44 winners and broke three times against the world-ranked 18 from Bulgaria.
Muller, 37th in the world, pulled ahead of Dimitrov 3-2 in their career series as he avenged a January semi-final loss in Sydney.
Swiss hero Roger Federer and rival Rafael Nadal are missing from the Basel tournament after both ended their seasons early to fully recover from injuries.
Top seed Stan Wawrinka was opening his assault later in an all-Swiss showdown with Basel wildcard and Federer childhood friend Marco Chiudinelli.