"Mo doesn't cut it loose all the time," a source said of Wilkerson, per Manish Mehta of the New York Daily News. "There's times when he takes a lot of plays off."
A year after tallying 12 sacks for the Jets, Wilkerson only managed 4.5 sacks in 2016.
Pro Football Focus broke down the drop in play from his Pro Bowl season in 2015 to last year:
The team believes it still can get him to reach another level with his play.
"He confuses being active with playing hard," a Jets insider said, per Mehta. "He thinks he's giving his all, but there's a difference between just giving effort and actually playing hard and playing all-out."
New York has made significant changes to its roster while releasing several veterans this offseason, including Darrelle Revis, Brandon Marshall and David Harris. Wilkerson remains on the squad thanks to his contract extension, but his five-year deal isn't fully guaranteed past this season.
Per Mehta, the team can release him next June and take just a $3 million cap hit, saving $17 million in the process.
When he is at his best, the defensive lineman is worth nearly any price thanks to his ability to impact both the run and the pass. Per Pro Football Reference, his approximate value in 2015 tied him for 10th in the league for all players, ahead of notable players like Khalil Mack, Aaron Rodgers and Richard Sherman.
The key for him will be to showcase a more consistent effort to return to being a dominant force on the Jets defense.