What's Going on with Miami Dolphins CB Brent Grimes?

Brent Grimes has one of the most difficult challenges in the NFL. Week after week, the Miami Dolphins ask their No. 1 cornerback to trail a team's best receiver all over the field. Understandably, this job has its ups and downs—you win some, you lose some—but for Grimes in 2015, it's been much more down than up, much more losing than winning. 

According to Pro Football Focus, Grimes has allowed 52 receptions on 78 passes thrown his way (66.7 percent) for 783 yards, five touchdowns, three interceptions and a 104.8 passer rating. 

On a per-snap basis, Grimes is one of the NFL's worst cornerbacks—or at least one of the cornerbacks with the biggest bull's-eye on his back. 

PFF lists Grimes with the third-lowest average cover snaps per target, the third-lowest cover snaps per reception and the third-highest yards per cover snap. Not only is Grimes targeted more often when he is on the field than almost any other cornerback in the NFL, but he also gives up receptions more often than almost any other cornerback. On top of that, he gives up more yards on those receptions than almost any other cornerback in the NFL.

Year	2013	2014	2015
Targets	98	95	78
Receptions	59	56	52
Catch %	60.2	58.9	66.7
Yards	730	706	783
Yards/catch	12.4	12.6	15.1
Touchdowns	0	7	5
Intercpetions	4	5	3
Passer rating	66.3	84.8	104.8
Pass break-ups	14	1	6

That's quite the step back from the 2014 season, when he allowed 56 receptions on 95 targets (58.9 percent) for 706 yards, seven touchdowns, five picks and an 84.8 passer rating on the season, or his shutdown 2013 season in which he didn't allow a single touchdown. What's changed?

For one thing, Grimes suffered a sprained MCL in Week 4 and a rib injury in Week 7, which could be slowing him down if either is still bothering him. He hasn't been listed on the injury report for a while, though, so that can't be the whole problem.

Grimes is getting older, too. At 32 years old, he's not the spring chicken he used to be. His speed allowed him to play physically at the line of scrimmage in his first two years with the Dolphins, because he could recover and run with a receiver stride-for-stride once they got into their route. These days, that skill isn't translating on the field quite the same way.

In the Dolphins' man-coverage-based scheme, those eroding skills are under a microscope. 

Against the New York Giants in Week 14, Grimes was targeted seven times and allowed six receptions into his coverage for 82 yards and a touchdown. But this isn't the only time he's been on the wrong end of some big plays. 

In fact, over the past month, it seems to be happening week...

After week...

After week.

And, of course, as mentioned earlier, there's a win-some-lose-some element to this discussion. After all, these are some pretty good players Grimes is going up against, and they get paid too. That being said, true No. 1 cornerbacks hold their own against those elite receivers. 

Grimes is due for a $9.5 million cap hit in 2016, but the Dolphins could save as much as $8.5 million of his cap hit if they cut him this offseason, and no less than $6.5 million depending on whether they designate him as a post-June 1 cut, according to Over The Cap.

Whether he stays or goes, the Dolphins might be in the market for a new No. 1 cornerback this offseason.