The Raiders placed O'Connell (thumb) on injured reserve Tuesday.
According to Vic Tafur of The Athletic, O'Connell could miss 4-6 weeks while he recovers from a broken thumb on his throwing hand. The Raiders haven't revealed whether O'Connell will require surgery to address the injury, but in his absence, Gardner Minshew will step back into the starting role. The Raiders signed Desmond Ridder off the Cardinals' practice squad to provide depth behind Minshew.