The pair are joined by Michal Golas and Peter Kennaugh, who relinquished his place at the Olympic Games because of a lack of form and fitness after breaking his collarbone in a crash at the Tour of California in May.
Spaniards David Lopez, Mikel Nieve, Xabier Zandio are also present, as is Irish champion Nicolas Roche.
Sky have never had a rider reach the podium in the hilly post-Tour Classic. Brit Adam Yates goes into the race as defending champion, with several riders, including Movistar's Alejandro Valverde, using the race as a preparation for the Olympics road race the following Saturday.
Team Sky squad for Clasica San Sebastian
Mikel Landa, Michal Kwiatkowski, Peter Kennaugh, Michal Golas, David Lopez, Mikel Nieve, Xabier Zandio, Nicolas Roche.
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