Gilbert was due to start in the Tour de Wallonie, but fell suddenly ill last week, suffering from chest pain and a fever, and the team was forced to start the race without him.
It was determined that the symptoms were due to a virus.
The BMC Racing team will also feature American Tejay van Garderen, who is fresh off his fifth place finish overall at the Tour de France, and the young Swiss rider Silvan Dillier, who finished third overall at the Tour de Wallonie today.
Also in the team for Clásica San Sebastián is Swiss rider Martin Kohler, Frenchman Amaël Moinard, American Peter Stetina and Belgians Greg Van Avermaet and Klaas Lodewyck.
BMC for Clásica San Sebastián: Silvan Dillier, Philippe Gilbert, Martin Kohler, Klaas Lodewyck, Amaël Moinard, Peter Stetina, Greg Van Avermaet, and Tejay van Garderen.