During his rehab, Mathis had 10 surgical procedures over an eight-month span to prevent infection and ensure that the Achilles was healing right, according to league sources. Doctors said they were amazed the 34-year-old Mathis suffered the number of setbacks he did, as well as the determination he demonstrated in overcoming them.
It is the reason why what normally is a six-month recovery period has taken a full year, and why Mathis -- who has 111 career sacks and led the NFL with 19.5 sacks in 2013 -- won't play until Indianapolis' home opener Sept. 21 against the New York Jets. He is officially inactive for the Colts' opener Sunday against the Buffalo Bills.
Mathis suffered the injury while training in Atlanta and serving a four-game suspension. He has said since June that his plan was to be ready for the start of the season.
ESPN.com's Mike Wells contributed to this report.