The Raiders expect to be without right guard Gabe Jackson for roughly eight weeks, Vic Tafur of TheAthletic.com reports.
Jackson injured the medial collateral ligament in his left knee, Tafur said.
After Jackson got rolled up on during the team period and left on a cart, coach Jon Gruden expressed “concern” about Jackson’s injury.
It doesn’t appear the Raiders will have Jackson for the start of the season. They also will be without left guard Richie Incognito, who will serve a two-game suspension to open the season.