The marriage between Buffalo Bills defensive end Mario Williams and head coach Rex Ryan didn't work out well in 2015, and after Williams' worst season in the NFL, he is ready to prove that he can get back to playing at a high level.

In Ryan's defensive scheme, Williams and his fellow edge rushers were asked to drop in coverage more often than they had under previous defensive coordinator Jim Schwartz. Williams had arguably the worst season of his career -- after racking up 27 1/2 sacks in 2013 and 2014, he finished with just 5 sacks in five games in 2015.

Via ESPN.com:

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"I'm prepared for anything because I know I'm going to prove a point and that is not even a question in my mind," Williams told ESPN NFL Insider Josina Anderson.

"At the end of the day, if I'm not there, I'll show you that I'm better than what I've been before. Like, that's just a chip on my shoulder regardless of whether I am there or not, because given the opportunity I'll get back to what I was."

Williams' struggles may not have been only due to Ryan's scheme. On 485 pass rush snaps, Williams finished with just 34 combined quarterback sacks, hits and hurries, per Pro Football Focus -- only five 4-3 defensive ends were less productive rushing the passer on a per snap basis.

Williams remains on the Bills' roster for now, but he carries a $19.9 million 2016 salary cap hit and the Bills can save $12.9 million of it by releasing him, according to OverTheCap.com. Earlier this offseason, Bills general manager Doug Whaley called the re-signing of free agents Cordy Glenn and Richie Incognito "imperative", and freeing up cap space by releasing Williams will help him get those contracts done.

Williams will enter his age-31 season in 2016, and he is just one year removed from an All-Pro season in 2014 where he racked up 14 1/2 sacks. If he hits the open market, you can expect him to be a priority free agent for every team that needs another pass rusher.