Unknown 20-year-old Cedrik-Marcel Stebe of Germany knocked 11th seed Nikolai Davydenko out of ATP Hamburg.

The Russian struggled to get going as world number 168 Stebe took the first set, and though Davydenko pushed the home crowd favourite to a tie break in the second set he ended up on the wrong side of a 6-3 7-6(5) scoreline.

Marin Cilic was forced to work hard for his victory in his second-round match at ATP Hamburg.

The Croatian came through a comfortable first set against German veteran Bastian Knittel, but lost the second on a tie-break and had to scrap his way through a decider before wrapping up a 6-3 6-7 6-4 victory.

Austria's world number 12 Jurgen Melzer also came through a battle against Spain's Daniel Gimeno-Traver, but turned on the style on the final set to win 6-3 5-7 6-1.

Top seed Gael Monfils of France cruised past Spain's Albert Ramos, winning 6-4 6-2, while evergreen veteran Radek Stepanek knocked out Italian 13th seed Andreas Seppi 6-1 7-5.

Former world top 10 player Fernando Verdasco came safely through his clash against fellow Spaniard Pablo Andujar 6-2 6-3, while world number 23 Janko Tipsarevic was knocked out by Juan Monaco, the Argentine easing to a 6-2 6-4 win over the Serb.

Eurosport