INDIANAPOLIS – For the next seven weeks, the Colts' offseason program is voluntary.

Optional.

Not mandatory.

That is how offseason programs have to be run, per the NFL's Collective Bargaining Agreement.

But as the Colts begin Week One of their "voluntary" work, they had all but a full locker room.

Attendance was nearly 100 percent and that's needed in 2016.

Since this Colts' regime took over in 2012, this year's offseason program is of the upmost importance.

Yes, this team is coming off an 8-8 season and missing the playoffs for the first time in four years.

The major reason why this time is so vital for the Colts comes from a new coordinator on each side of the ball.

Classroom work is in the "101" stages for the Colts' offense and defense.

"This is a time where you ask a ton of questions," D'Qwell Jackson, the Colts' defensive signal caller, said on Monday afternoon.

"You ask the simple questions. You don't assume that anyone knows anything. The quicker we understand the concept of what we are doing, the better off we will play."

Jackson has been in this sort of situation far too many times than he would like in his 11 NFL seasons.

His early introductions to Ted Monachino's defense have him excited.

When Monachino was first hired in January, Chuck Pagano reached out to his defensive leaders to let them know what they were getting.

"I know Chuck and I know what style of football he wants to play defensively and that's to play attack style and to be aggressive," Jackson says. "For the guys that are pass rushers, it's a different mindset if you know you're going to have your fair share of times you are going to rush and get after the quarterback. You lick your chops. For the DBs, it helps them. They don't have to cover as long. For myself, things open up that wouldn't normally open up when you have a pass rush.

"The question was what type of defense are we going to run? 'We are going to attack. We are going to play aggressive football.' That was all that needed to be said."

Flip over to the offense, and Rob Chudzinski is now able to offer the full installment of his system.

It's this "voluntary" classroom time that has to be ingrained before the 11-on-11 work begins.

"There's certainly a different learning aspect and it's learning a new offense," Andrew Luck says.

"You have to learn the new language and that started (Monday). There is carryover but it's like learning a language. You have to sit down and sort of build a foundation and build some fundamentals and go from there. The guys we brought in will be great teachers. I know we're relying on each other as players, too, to make sure that we hold each other accountable in learning the new system and getting it down pat."