Quality Slovak Martin Klizan was among Monday's opening-round winners at the $530,000 Mercedes Cup tennis event.
The eighth-seeded world No. 38 whipped Spaniard Albert Montanes 6-2, 6-3 on the red clay at Weissenhof Tennis Club. Montanes titled here in 2010.
Also on Day 1, German wild card Michael Berrer got past Spaniard Daniel Gimeno-Traver 6-4, 3-6, 6-1, while Spain's Roberto Bautista Agut beat German Tobias Kamke 6-3, 7-6 (7-4).
This week's top seeds are German favorites Tommy Haas and Philipp Kohlschreiber. Haas was a Stuttgart finalist back in 1999.
Serbian Janko Tipsarevic topped Argentine Juan Monaco in last year's finale.
This week's big winner will take home $110,000 and a brand new Mercedes-Benz sports car.