What happened to Peterson?

Talk about an off season... Last season he was the go-to guy. He had over 1,300 yards. He topped 100 receptions. It was a big year. His first two seasons with Edmonton he topped 1,000 yards.

But this season... yikes. He's sitting at 689 yards. I doubt he'll hit 1,000 yards this season. He'd have to average 78 yards/game, and considering he's only had 3 games with 70 or more yards, I just don't see it happening.

So what happened? He looked so good. Is he just having an off year, or has Stamps officially passed him as the go-to guy?