INDIANAPOLIS -- The biggest offseason checklist for Chuck Pagano -- if he returns in 2017 -- deals with the area he was supposed to be an expert in when he joined the Colts in 2012. And it’s where they have routinely failed under Pagano's leadership during the past five years.

Defense.

Note: Pagano’s status as coach of the Colts, to me, will remain in the air until owner Jim Irsay ends his silence and officially says Pagano will be back for Year 6.

Pagano’s defense, which has featured two different defensive coordinators in his five seasons, has finished 20th or worse in four of those seasons, including a pitiful 30th this season. The 6,126 yards they gave up in 2016 are the most they’ve surrendered since the team moved to Indianapolis in 1984. Pagano's unit is responsible for the three worst years in Indianapolis. They gave up an average of 382.9 yards this past season, 379.1 in 2015 and 374.3 in Pagano's first season in 2012.

“That falls on me,” Pagano said. “You guys know my background, and everybody knows my background, and we’ve fallen short. Again, we won’t make any excuses. We’ve got some really good football players and we’ve lost some good football players, and we’ve made our mistakes. It’s the National Football League. I’ve made obviously a ton, my fair share. I’m accountable, and I can accept that responsibility. Again, we’ll look at everybody, evaluate everything that we have done, evaluate where we’re at and see how we can improve.”

It’s easy to be a successful defensive coordinator like Pagano was during his time in Baltimore when he had Ray Lewis, Ed Reed and Terrell Suggs. It’s not easy to do it when you have only a few talented players each year or an aged unit like this season. The Colts have lacked a difference-maker in the pass-rush department since Robert Mathis had 19.5 sacks in 2013.

That’s why they have to put as much focus in finding linebackers, pass rushers and a second cornerback as they did in emphasizing improvement in their offensive line last offseason.

The Colts’ best defensive player, linebacker Erik Walden, who had 11 sacks last season, is a free agent. Will general manager Ryan Grigson draw a line in the sand on how much he’ll pay Walden the way he did with linebacker Jerrell Freeman last year?

Grigson’s stance led to a revolving door at middle linebacker with Nate Irving, Sio Moore, Josh McNary and Edwin Jackson, and it was more of a mess than a success.

Mathis and his 123 career sacks called it a career after 14 years, and Trent Cole is a free agent. The status of D’Qwell Jackson, who closed the season with a four-game suspension for using performance enhancement drugs, is murky because he’s 33-years-old and clearly isn’t the same player. Jackson still has another year left on his contract.

Meanwhile, Vontae Davis is still looking for a second cornerback to play alongside him because Patrick Robinson was basically Greg Toler II, a player who showed flashes at times, but was hurt way too often to make an impact.

So If Pagano is back next season, he needs to be in the ear of Grigson -- if he’s also back. And they'll need to utilize that part of the $60 million in salary cap space that they have and a good chunk of their draft picks need to be used on defense.