The Serbian world number two eased through the first set 6-1 but lost a second-set tie-break to the German 7-3.
However the third set was again comfortable as he set up a meeting with Carlos Berlocq.
David Ferrer, seeded second and world number five, retired when he was trailing 5-4 to Taiwanese Lu Yen-Hsun.
Seventh-seeded German Tommy Haas also went out at the first-round stage 6-4 4-6 6-2 to Russia's Mikhail Youzhny, who is ranked seven places below him in the ATP list at 28th.
Third seed Jo-Wilfried Tsonga of France beat Uzbek Denis Istomin 4-6 6-1 7-6(3). Next up for him is Nikolay Davydenko after the former world number three won 7-5 6-1 over fellow Russian Alex Bogomolov Jr.
Richard Gasquet, who won the title in Bangkok on Sunday, defeated Matthew Ebden 6-2 6-4.
It was a third consecutive straight sets victory for the French fifth seed over the Australian qualifier. Gasquet breaking his opponent six times in an 81 minute victory.
Andreas Seppi went through after Julien Benneteau retired in the second set with the scores at 6-1 2-0, Feliciano Lopez defeated Ryan Harrison 7-6(3) 5-7 6-2 and Jurgen Melzer beat Pablo Andujar 6-1 4-6 7-6(3).