Korster left the field on a stretcher in the first-half and is set to undergo scans this week to determine the severity of his injury. Chavhanga was barely on the field before he, too, got injured.
It means Stormers coach Rassie Erasmus, hoping to improve on his side's current mid-table standing, could have to shuffle his back division for the upcoming games against the Crusaders, Waratahs, Brumbies and Highlanders.
"When Nick got injured it was a bit of a blow for us, but we thought, okay, we had a world-class wing to put on, but within five seconds he pulled his hamstring," said Erasmus.
"Obviously, they are both in doubt for the Super 14 tour. You know now the squad system, with the 36 guys starting the pre-season, needs to help us."