That would be an OK explanation if his prodcution was a little off, but he was terrible. He caught 6 passes in 8 games. He was on the bench behind stiffs.
For those 8 games he probably had the least recpetions per snaps played of any WR in the entire NFL, and if it wasn't the least he was only behind some stiffs.
I was exclusively addressing the speed issue wrt his age and health. There are a lot of other potential reasons for his performance being terrible, not the least of which is his attitude (possibly a result of other Titans' offensive and coaching issues, at least in part).