INDIANAPOLIS -- The Indianapolis Colts' decision to give linebacker Robert Mathis a contract extension Tuesday came as a surprise.

Based off Mathis’ 2013 stats -- an NFL-high 19.5 sacks -- he deserves every penny of the 2016 extension that could pay him as much as $6 million.

But nobody knows if Mathis will be that same player when the 2016 season rolls around. Nobody even knows if he would be that player today because he’s not on the field chasing down opposing quarterbacks and getting strip sacks.

First there was the four-game suspension for using performance-enhancing drugs that kept Mathis off the field, and now a torn Achilles, which happened while he was working out during his suspension, has him out for the rest of the season. The Colts have decided to pay Mathis the remaining portion of his $2.3 million base salary this season when they didn’t have to because his torn Achilles is categorized as a non-football injury. Mathis returned to the team's facility Monday.

Mathis will be 34 years old and coming off a torn Achilles at the start of the 2015 season.

Shortly after his injury was announced earlier this month, I talked to ESPN injury expert Stephania Bell about the road Mathis has ahead of him. He’s looking at about a six- to nine-month rehabilitation period.

“It always gets harder to return from these big injuries as you get older, but let me say this: Age isn't the full factor,” Bell said. “... It makes it harder because your body doesn't recover as quickly. Even in the day-to-day rehab it can be taxing and your tissue is a little more brittle with age. You're summing up the history of all the abuse your body has taken over the course of your professional athletic career. That total of the wear and tear will factor into what you have to deal with coming out of surgery.

“I'm not saying you can't have a comeback or can't return to a top level of play. The history of being an athlete at that age, you're going to show some decline as an elite athlete as you get into your 30s with or without an injury. There are some guys in their 20s who struggle to come back from Achilles tears. It's a tough injury. Then there are guys in their 30s who will recover and come back in top form. Age isn't the full factor, but it certainly is one of the factors that makes it little more difficult.”

The Colts have a saying they like to use inside the organization: "Trust, loyalty and respect." They backed up that statement in giving Mathis an extension with the hope he'll be able to continue terrorizing quarterbacks.