The veteran outside linebacker told a local television station he intends to be back on the field by the first month of the 2015 season.
Mathis missed all of 2014 after suffering a torn Achilles tendon during a private workout last September. Mathis suffered the injury while serving a four-game suspension for violating the league's performance-enhancing drug policy.
Mathis' proclamation comes after Colts owner Jim Irsay raised eyebrows in March by saying Mathis could be sidelined until November in a worst-case scenario. ESPN reported that Mathis had suffered a setback in his recovery process, though Mathis' agent denied it.
"I'm back running. Training and rehab (are) full swing," Mathis said. "I'm ahead of schedule and just trying to stay ahead of it. Guys view me as their leader and I'm busting my hump to get back out there with them because it wasn't easy to sit back and watch them play without me."