The thing about Sharp is that virtually none of his underlying stats paint the picture of a man in any sort of decline. All of his possession stats, assist rates, shot generation rates, scoring chance generation rates and defensive stats like shot suppression are all pretty much in line with career averages. If any of those numbers were falling, I’d be a lot more concerned. The only thing that really fell off a cliff was his shooting percentage, which thankfully is something that is very prone to variation and often a better indicator of bad luck as opposed to a failing skill set (at least when the fall is so massive). He also received under 17 minutes of ice time in 14/15 (by comparison, that is less then Cody Eakin received) so that is certainly another big reason for his goal totals falling off.
Thankfully, the Hawks are a team that has a lot visibility and I can watch them a lot. To me at least, Sharp still looked to have a great skill set, his shot was still very nice (I remember him scoring a laser from the point and another game winner against the Stars in particular), he still looked to be a very good skater and his all-around game still looked to be quite impressive and something the Stars really missed.
Of course all hockey players decline and betting that a player will likely be worse in his mid-thirties then when he did earlier is usually a pretty safe bet. But I don’t think his decline will be any worse than average, I actually think it will be slightly better than average. For me at least, I am very comfortable projecting him to score at least 25 goals and around 55 points (significant injuries not withstanding). And if he can get anything close to that without his defensive skill set falling off, I think he will be well worth the transaction, his salary and a spot flanking Tyler Seguin.