If there’s one truism in the NFL, it’s that a player can always become who he was four or five years ago with the right coach. Or maybe I just made that up entirely.

But with the semi-spiral that Dawan Landry finds himself in, a reunion with Rex Ryan — his former defensive coordinator in Baltimore — is something to feel good about. Unfortunately, it may be the only good feeling the Jets get with this signing.

The Jets signed Landry to a one-year deal this afternoon, and he’ll now be asked to replace his brother LaRon, the man with cinder blocks for arms who departed for Indianapolis. The older Landry (Dawan is 30, and LeRon is 28) doesn’t pack the heavy punch that his brother does, put he has sturdier bones, which is nice. Dawan hasn’t missed a game since 2008, a time when he was experiencing his best years in Baltimore after being a fifth-round pick by the Ravens in 2006.

The problem, though, is his coverage ability. That’s not an ideal problem to have when you’re asked to mostly, you know, cover people.

Landry comes over from the Jaguars, and their secondary which allowed 239.5 passing yards per game (22nd). That high volume of opponents running in the open field led to his career-high 100 tackles. But the most troubling number associated with Landry is the 107.4 passer rating opposing quarterbacks had on balls thrown in his direction, according to Pro Football Focus, and only six safeties fared worse during the 2012 season.

In fairness, Landry was often left to flail helplessly when he as given very little support from a Jags pass rush that registered a league low 20 sacks. So there’s hope for a return to average, which would be a gift on a secondary that lost more than just Dawan’s bro at safety, with Eric Smith and Yeremiah Bell gone too.