Tampa Bay running back Doug Martin has been suspended four games for violating the NFL’s policy on performance enhancing substances and said Wednesday he’s entering a treatment facility rather than appeal the ban. "On the field, I must be strong and determined to push through both pain and injuries to become an elite NFL running back. Off the field, I have tried that same approach in my personal life. The 27-year-old signed a five-year, $35.75 million contract, with $15 million guaranteed, in the offseason after finishing second in the NFL in rushing in 2015 with 1,402 yards.