2. CB Jerry Jacobs
Jacobs had a rough start this season, then he turned it around for a few games (see two interceptions against the Packers in Week 4, and another against the Carolina Panthers in Week 5). But he has not really stood out since, and the loss in the rematch against the Packers looks like a low-point.
According to Pro Football Focus (h/t to Kyle Meinke of MLive), Packers quarterback Jordan Love targeted Jacobs nine times on Thanksgiving Day. That was nearly twice as much as anyone else, among Love's 32 pass attempts, and eight of those targets were completed for a total of 101 yards. Jacobs was the second-worst graded Lions' defensive player in the game (40.6 overall grade), and he's now PFF's 77th-ranked cornerback for the season (pending the rest of Week 12 of course).
Ideally, free agent signing Emmanuel Moseley would have been the other starting cornerback for the Lions opposite Cameron Sutton this year. But it was not to be, with a second surgery on the knee he tore the ACL in last season, then an additional hamstring injury and finally tearing his other ACL two snaps into his Lions' debut.
So Jacobs, as solid as he had been over his first two seasons, won and has kept the starting job practically by default. Will Harris is a far worse player than Jacobs, and nowhere near starter-caliber, Undrafted rookie Steven Gilmore has played in three games, with just two defensive snaps. Khalil Dorsey is fine in his role on special teams, but starter-level snaps as an outside cornerback would be a heck of a step up.
So, if only for lack of better or more proven options, Jacobs will not be benched and he'll be left to figure it out moving forward. But he surely would be benched if there were another viable option, even it could be argued if he deserves to be benched or not.