INDIANAPOLIS – Training Camp move-in day is less than a handful of days away for the Indianapolis Colts.
With that, our "Burning Questions" series turns to the defensive side of the ball, with an experienced linebacker group waiting in 2015.
Here's a look at the linebacker burning questions heading into the 2015 Training Camp:
When should Colts fans expect Robert Mathis to be back on the field?
The injury watch of Robert Mathis is the clear No. 1 storyline heading into Training Camp, after Gosder Cherilus was released on Sunday.
Video of Mathis working out seem to indicate that the Colts all-time sack leader is very close to returning to the field. Jim Irsay reiterated on Monday that Mathis is progressing, but has not been cleared yet.
Chuck Pagano is scheduled to meet with the media on Sunday so the next Mathis update could come then, a few hours before the Colts have their first Training Camp practice of 2015.
Let's say best-case scenario, and Mathis is ready to go by the season opener (which No. 98 has made it clear to be the time table).
The Colts will have ample outside linebacker depth.
Maybe the most important part for the Colts is that they will not have to feel the need to play Mathis every defensive snap.
A pitch count on the reps for Mathis would obviously help the 34-year old pace himself, after missing the entire 2014 campaign.
I do think it's important for Mathis to test out his Achilles at some point in Anderson to see just where he's at, and how the Colts can then judge his workload leading into the regular season.
STAT TO NOTE: In his last 92 games, Trent Cole has recorded at least one quarterback hurry in 90 of those contests.**
Will Nate Irving challenge for a starting inside linebacker position?**
When the Colts begin Training Camp later this week, D'Qwell Jackson and Jerrell Freeman will be the starting inside linebackers.
That will likely be the case until Nate Irving can find his way onto the field.
Irving tore his ACL midway through last season, ending his year after starting the first eight games for the Denver Broncos.
The Colts added Irving in free agency, with the intention that he would compete for a starting spot (when healthy).
Even if Irving doesn't start for the Colts in 2015, he still should play a major role for a unit striving to stop the run better.
For different reasons from Mathis, having Irving on the field during camp is critical.
Irving needs to learn the defense in actual offense/defense settings, something he could only replicate from a mental standpoint during the offseason program.
His impact might not be felt in September, but Irving could definitely factor in quite largely to the success of the Colts defense in 2015.
STAT TO NOTE: D'Qwell Jackson's 138 total tackles last year were the most in the AFC.**
Who could make up the Colts pass rushing packages on third-down?**
This is where Greg Manusky should sleep much easier at night, compared to past years.
Outside linebacker options (pending a healthy Mathis) should not be an issue for the Colts in 2015.
Even without Mathis in 2014, the Colts still had 41 sacks, one behind the number Mathis and the pass rush produced combined for in 2013.
Getting more and more creative in 2014 now includes some talented pieces to that puzzle in 2015.
Guys like Mathis and veteran Trent Cole are the obvious proven edge guys.
Second-year outside linebacker Jonathan Newsome led all rookie defensive ends and outside linebackers last season with 6.5 sacks.
Those three guys could be on the field together in obvious passing situations this season, forcing offensive protections to quickly decipher how they want to block the Colts edge rushers.
A healthy Mathis in 2015 is going to give Manusky options that Pep Hamilton has with all of his different skill guys.
STAT TO NOTE: Jonathan Newsome's 6.5 sacks in 2014 were the most for any rookie defensive end/outside linebacker last season.
2015 Linebackers (17): OLB-Daniel Adongo (2 Years), OLB-Trent Cole (11 Years), ILB-Carlos Fields (1 Year), ILB-Jerrell Freeman (4 Years), OLB-Cody Galea (Rookie), Amarlo Herrera (Rookie), OLB-Zack Hodges (Rookie), ILB-Nate Irving (5 Years), ILB-D'Qwell Jackson (10 Years), OLB-Cam Johnson (3 Years), OLB-Robert Mathis (13 Years), ILB-Henoc Muamba (2 Years), OLB-Jonathan Newsome (2 Years), ILB-Justin Shirk (Rookie), ILB-Junior Sylvestre (Rookie), OLB-Erik Walden (8 Years), OLB-Bjoern Werner (3 Years).Roster Outlook*: Last year, the Colts kept nine linebackers on their 53-man roster after the preseason. To me, the linebacker position is definitely the deepest on the defensive side of the ball. While inside linebacker doesn't have a ton of depth, the outside linebacker spots will have to cut ties with players who could very well latch on with some other team. The injury outlook for Robert Mathis and Nate Irving could impact the depth at each linebacker spot coming out of the preseason.[
ICYMI: Quarterback Burning Questions*](http://www.colts.com/news/article-1/Jim-Irsay-Robert-Mathis-Not-Cleared-Yet/380ebe6f-bfbe-40af-9143-ffb815bc5a47)