Yeah, I do think injuries can be a sign of decline, especially if they are chronic things.
Regarding our injuries: Solder's injury was a torn bicep, which is usually a sign of over-training and hopefully not a sign of things to come (touch wood). But Vollmer's injuries are wear and tear type of injuries that are a sign that he's just running to his end. Lewis has a long injury history, and that's a just risk we've got on the roster. You can't win games from the trainer's room. Mayo's injuries were the type of chronic thing that ends careers, and lo-and-behold, it ended his career; and we replaced his roster spot with McClellin + Bostic + rookie, any of which may or may not pan out.
The Pats have a different approach to roster building than most teams, with regards to handling injuries. BB rarely spends top dollar on a veteran free agent all-pro starter, but he will spend top dollar on the no-name journeyman backup who can step in and fill a gap after the starter rips his ACL. The result is that despite a crazy mess of injuries all over the roster, the 2015 team still made the AFC Championship game and nearly won it.
Over 10 years, Brick showed no sign of wear, whatever you think of his "declining game". And from my seat, until he refused to take a pay cut and abruptly retired, I have no memory of Jets fans clamoring to bench the guy or trade him to anyone who'd take him for loose change and a bag of chips, because his declining game was a big deal. So I wonder how much of his "decline" is really just sour grapes now that he's gone? As a Pats fan, I perceived that the guy was a rare cornerstone on the roster along with Mangold, Wilkerson, Fitz and Revis, for a team that could use a few more cornerstones.
Clady is talented but unreliable... and unreliable just in these last few years. How much of his rep is based on old news? The Broncos didn't sell on him for a 5th-7th round swap because they felt he was at the top of his game and rising. What if you lose Clady in Week 3, what happens to your team then? If I'm the Jets GM, I fill Brick's roster spot with Clady in a bit of a panic, and now I need to spend a little more money on the depth chart behind him because I'm just not 100% sure he can play 19 games.
Is that really an upgrade? Feels like a Push to me, at best.