How does that prove there was a decline in play? He can't throw it to himself. We know who the QB was locked into.
It's pretty simple math. Now, you can say that Lamb was the reason for it. You can say that Dak was the reason for it. But the numbers here and in Houston his last two years (with different QBs and different lead receivers) show a decline in play. You don't go from being a 1,000-yard receiver to a 650-700-yard receiver without a decline in play. Before, teams had to throw him the ball because his skills demanded it. Not so much the last two years.
That doesn't mean he isn't still fast, can't get open, etc., it just means his production has fallen off. Whether he's the main reason for that is something we'll find out. Frankly, I think he's at a point in his career where he'd be better served being a third receiver, that speed threat that teams can't focus on because of the No. 1 and No. 2 guys, but that isn't going to happen here.
I'm curious, since you don't seem to believe the stats don't prove a decline in play, what do you have as evidence against a decline in play? I mean, you can say you don't see it, but if you have no measurable numbers to prove there isn't one, I think the two straight seasons below 1,000 yards say there is.
It's kind of like Ezekiel Elliott. I believe injuries midway through his last two seasons with us affected his play. I believe the line play in New England and a poor passing game affected his average. However, anyone who believes he's hit the wall has 3.8 and 3.5 averages to lean on as proof, and I can't refute that. It's up to him to show that he's better than that, just like it is up to Cooks to show that the wear-and-tear wall isn't bringing him down.