Doug Martin had an outstanding year. This is not news. What is news is that he did so against primarily base defenses -- he wasn't helped much by facing pass defenses, as chronicled by Pro Football Focus.
Doug Martin enjoyed a resurgence in 2015 and this study suggests that he was even better than his raw numbers suggest. Of Martin's 288 carries, 78 percent came when the defense had fewer than five defensive backs on the field. That's the league's fourth-highest mark. Martin averaged 4.8 YPC vs base defenses (10th best) and 5.6 YPC vs. nickel (fourth best). Martin picked a fine season for a career year as he's now headed to the open market.
If Martin moves on, the Buccaneers won't have trouble finding his replacement. Charles Sims is far from a household name, but he was one of the league's most-effective backs in 2015. Unlike Martin, Sims benefited from handling most of his carries against nickel and dime defenses (62 percent - 10th highest). Like Martin, he easily outperformed his expected YPC. Sims averaged a solid 4.4 YPC vs base defenses and 5.8 YPC vs nickel (third best in the league). Sims might be best suited as a committee back, but he's earned himself a shot at feature back duties.
That makes Martin's performance even more impressive than it already was. There are genuine question marks with Martin, mostly related to his pay and the reason for his replacement-level performance in 2013 and 2014, but his performance last season was simply outstanding by every measure.
I'd disagree with Pro Football Focus that Sims deserves a shot as the team's feature back. No one in the NFL "deserves" a shot at anything -- and while Sims was outstanding, Martin was more reliable and more productive against base defenses. That's where a back in the Bucs' system has to make his money: as the early-down player who can grind out yards with consistency. Martin can do that. Sims hasn't shown he can, and relying on him to do so is likely a mistake.
There's plenty of time left for the Bucs to re-sign Martin, even if recent reports haven't been very encouraging. These numbers should help Martin's agent in finagling a high-paying contract out of someone -- perhaps someone other than Jason Licht.