Del Potro reached the final at Indian Wells last week, but was unable to see off 89th ranked Kamke.

CNN: Injury heartache for Williams at Miami Masters

Defending SAP Open champion Milos Raonic beat his predecessor as ATP Newcomer of the Year, Tobias Kamke of Germany, to reach the quarterfinals.

CNN: Monfils pulls out as Roddick battles through in San Jose

Federer will play home favorite Julien Benneteau in the next round after the Frenchman prevailed 7-6 7-5 5-7 0-6 6-4 against Germany's Tobias Kamke.

CNN: Cash: Only injury can deny Nadal in Paris