SANTA CLARA, Calif. — Blaine Gabbert is back on the field for a second chance with all the skeptics figuring he can’t begin to fix a problem that goes far beyond the quarterback position. Colin Kaepernick had his opportunities and then some for San Francisco, and he’s headed to the bench after failing to deliver week after week. The turmoil inside Levi’s Stadium hit new levels this week as the 49ers (2-6) prepared for the Falcons with a new man under center in Gabbert behind a shaky offensive line that has done little to protect the quarterback.