Colston's athleticism is all but gone at this point but I've also noticed that he isn't nearly as sure-handed anymore. I noticed it last year and also in a recent preseason game where he had a gimme in the end zone but just let it slip through his hands.
Here are his most recent catch rates percentages..
2011 - 75%
2012 - 64%
2013 - 68%
2014 - 60%
Not coincidentally, his RZ efficiency has seen a similar decline..
2011 - 13 RZ targets, 10 reception (77%), 4 TDs
2012 - 23 RZ targets, 17 receptions (74%), 10 TDs
2013 - 16 RZ targets, 8 receptions (50%), 3 TDs
2014 - 13 RZ targets, 6 receptions (46%), 3 TDs
I think Colston is rapidly approaching the cliff and I'm left wondering how targets are going to be distributed this year, especially at the beginning of the season if Spiller misses time. Graham specifically accounted for 26% (on average) of NO's RZ targets during his tenure and I highly doubt those all go to Watson/Hill.
Coleman is a big dude, fast for his size (similar to Benjamin) and will potentially find himself in a great situation this year. Due to the upside he's one of my favorite late round grabs this year.