Stuttgart, Germany -- (Sports Network) - Seventh-seeded Argentine Jose Acasuso was among the opening-round losers at the Mercedes Cup, where Wimbledon and French Open champion Rafael Nadal announced his withdrawal on Monday.

Just one day after beating Roger Federer in a classic Wimbledon final, Nadal made the trip to Stuttgart to announce he was skipping this week's event due to a knee injury.

Nadal was the top seed here and beat Swiss Stanislas Wawrinka in last year's Stuttgart finale. The world No. 2 Spaniard also titled here in 2005.

Meanwhile, Spaniard Albert Montanes toppled Acasuso in 6-3, 7-6 (7-5) fashion on the red clay at TC Weissenhof, while Andreas Beck snuck past fellow German wild card Daniel Brands 3-6, 6-3, 6-4 and German Michael Berrer handled France's Eric Prodon 6-3, 6-4.

Additional wins came for Argentine Juan Martin Del Potro, Uruguay's Pablo Cuevas and Spaniard Oscar Hernandez.

This week's titlist will collect $185,000.