Mathis tore the Achilles tendon in his left foot in September 2014 while he was serving a four-game suspension for violating the league's ban on performance-enhancing substances.
The 34-year-old six-time Pro Bowler last played during the 2013 season, in which he led the NFL with 19.5 sacks. He has two seasons left on a four-year, $36 million deal he signed in 2012.
"It's hard to say," Irsay said, according to the Indianapolis Star. "We want to make sure the doctors feel he's ready. And that re-injuring and that sort of thing is not going to be a problem. We've talked about kind of October, roughly. Can he come back quicker than that? Knowing Robert, anything is possible. I really just don't think he's going to be ready for the Buffalo game at the start of the season."
Although Irsay put a timetable on the return of the franchise’s all-time sack leader, Mathis himself said in June that he would be ready when the regular season opens Sept. 13 against the Buffalo Bills, adding that he was ahead of schedule in his rehabilitation.
Whenever Mathis returns, Indianapolis looks to improve on defense after giving up 23 points a game last season, including 45 points and 177 yards rushing in a rout at the hands of the New England Patriots in the AFC championship.
"We're looking to prove we can be a consistent defense, that we can stop the run, that we can put pressure on the quarterback," Irsay said. "I know our guys are motivated to have a great year. And there's playmakers on that side of the ball, no question."
- Scooby Axson