Hernandez definitely did not have as good a season in 2012 as he did in 2011. He caught a lower percentage of passes thrown his way (60.7% vs. 69.9%), as ivan detailed in the opening post, and also dropped 10 passes, the 2nd highest total in the NFL (to Graham's 15) among TE's, but the highest drop percentage among the 21 TE's targeted 50%+ of the time, 16.4%. This compares to only 5 drops and a 5.9% drop percentage in 2011.
The question is, how much of Sweet Leaf's drop off can be attributed to injury, how much to skill, and how much to not having Gronkowski on the field? My sense, although there is no way to definitively prove this, is that injury played a huge role in Hernandez' 2012 down season.
In 2011 he was ranked very highly by all of the available advanced football metrics. Football Outsiders placed him as the 9th best TE in football according to Defense Adjusted Yards Against Replacement (DYAR - explanation here
), while Pro Football Focus rated him the 5th best TE in the game (their rating system can be found here
). Whether you believe these metrics or not, and there is good reason to be skeptical (although it is worth noting that one Rob Gronkowski was by far the best TE according to both sites in 2011), it still is clear that Aaron Hernandez had a great 2011 season at the age of 21/22. He caught 76.5% of the passes thrown his way in the slot in 2011, 2nd best among TE's, and gained 1.9 yards per route run, the 4th highest total for a TE. His 2012 ratings on both advanced stat sites were way down (Gronk was first on both again, although not by as great a margin), as were his reception percentage and drop percentage, but, again, he was dealing with injuries all season.
Hernandez is versatile player who has accomplished much at the age of 23, and has, imo, tons of untapped potential. There is no way I would consider trading him