The four starters in the secondary are set, and that first unit of Rashean Mathis and Darius Slay at corner and James Ihedigbo and Glover Quin at safety has played well. They have ceded just one field goal in five full preseason series.
Behind the underrated starting unit, the depth chart remains highly unsettled.
Presumed nickelback Bill Bentley, who has held that role for most of the last two seasons, has struggled both in camp and the preseason games. Pro Football Focus (subscription required) grades the 2012 third-round pick harshly, his minus-3.4 weighed down by two penalties.
Bentley's draft classmate, Jonte Green, has struggled even more. The Raiders engineered their comeback win largely by targeting Green, as noted by Nathan Jahnke of PFF:
For one reason or another, late in the game the Raiders choose to target Green relentlessly. In his 17 plays in coverage, his receiver was targeted 11 times. While his numbers will show he only allowed four completions, that doesn’t include a few times where he was beat in coverage but there was a bad throw or a dropped pass. Those account for a number of the incomplete passes and not strong play from Green.
He's had some positive moments in training camp but not enough to inspire any confidence. The third corner from that 2012 draft class, Chris Greenwood, is trying to seize upon those struggles to assert his own case for regular-season playing time.
Greenwood has been uneven as well but has outplayed Bentley and Green. I broke down his performance vs. Cleveland with harsh eyes, but he's been the best of the trio. He had little to do in limited action in Oakland, which might actually augment his chances.
The team brought in Drayton Florence to try and provide a veteran solution, but he was terrible against the Raiders. He bit hard on a hitch-and-go by Bryce Butler on 3rd-and-10 and was barely visible in the picture as the Raiders roster long shot hauled in a 38-yard bomb.
Former Colts starter Cassius Vaughn has been the best of the reserves throughout camp, though he's just one full season removed from being the worst corner in the league per PFF.
The picture is a little clearer at safety, though the competition between Isa Abdul Quddus, DeJon Gomes, Jerome Couplin and Don Carey remains undecided. Abdul Quddus and Couplin should have the edge based on preseason play, but that might not be how the coaches see the field.