Former world number eight Janko Tipsarevic shocked Bernard Tomic to progress to the second round of the BMW Open.
Wild card Tipsarevic came from behind to clinch a 5-7 6-1 7-6 (7-3) win over the sixth seed.
The Serbian saved a match point when serving at 5-4 down in the decider and won the next two games to set up a second-round clash with Victor Estrella.
While Tomic fell at the first hurdle, the three other seeds in action on the clay in Munich all progressed in comfortable fashion.
Fifth seed Philipp Kohlschreiber beat Jiri Vesely 6-1 6-2 at his hometown tournament, while eighth seed Fabio Fognini overcame Bastian Trinker 6-2 7-6 (7-3) and ninth seed Lukas Rosol needed just 54 minutes to dispense of Florian Mayer 6-2 6-2.
Dominic Thiem saved two match points as he battled to a 5-7 6-4 7-6 (11-9) victory over Vasek Pospisil after a hard-fought contest that lasted two hours and eight minutes.
Qualifier Mischa Zverev will take on world number three Andy Murray in the second round following a 7-6 (8-6) 3-6 6-4 triumph against Jan-Lennard Struff.
Elsewhere in the draw, Sergiy Stakhovsky double-bageled Mikhail Ledovskikh 6-0 6-0 in a mere 35 minutes. There were also wins for Radek Stepanek and Simone Bolelli versus Farrukh Dustov and Dustin Brown respectively.