Luxembourg’s Gilles Muller has posted his 100th singles win by hammering 14 aces past Australian Marinko Matosevic in the opening round of the ATP Tour’s Atlanta Open on Monday.

Muller improves to a 12-14 on the season with the 7-6 (7-5) 6-4 victory and moves on to square off against two-time defending champion Mardy Fish of the US. Muller is a former US Open quarter-finalist.

Meanwhile, American wild card Jack Sock defeated seventh seed Alex Bogomolov 6-2 4-6 6-4.

The 19-year-old Sock converted two of his three break points while saving six of the seven chances he faced on serve in the two hour, 15 minute match.

Russia’s Bogomolov has now lost five consecutive matches and falls to 9-21 on the season.

Sock is no stranger to winning lower-level matches as he captured the US Open junior doubles title in 2010 and the mixed doubles crown in 2011.

He is now trying to raise his game to the highest level, and in order to help him do that, he recently hired former world top 10 player Joakim Nystrom as his coach.