Raiders are most likely to finish at 7-9, with a likely win vs Denver and likely losses vs. Indy and @KC. Slight chance of 8-8, but I can't see them winning or losing out.
At 7-9, their highest finish is likely #15. There are 5 other non-playoff teams above them that will likely stay above them: Indy (or Jac), Tampa, Miami, SD (or KC), and GB. Even if the Raiders finish strong at 8-8, those 5 teams are still likely to finish above them.
Also, there will likely be at least 2 other 7-9 teams. I looked at the remaining games for all the teams with records close to Oakland's. Can't tell at this point how the tiebreakers would fall.
All in all, we have about a 90% chance of picking between 13 and 15, so if you had to guess a specific number, it would be #14 imo.