Okay let's look at this by position group, because I clearly don't have a clue as to what I am saying* :
Defense
MLB - If Grace or Schmidt take over they warrant a shot. If it becomes Morgan, not so much.
WLB - Is going to be Smith, and he is definitely a "tweener." Has the skill and is showing the leadership but is a sophomore. If I were the coaches I would at least wait until next year to encourage development of his game this year, and to encourage him to come back a fourth year (I know that isn't a whole lot of encouragement when you have bazillions of NFL bucks staring you down.)
SLB - If Councell takes over, in other words, takes the majority of snaps run or pass, and only yields for special packages, he would be a really good choice for a second defensive captain. Ben taking over the strong side would be a very important step in this defense becoming very good, quickly!
DT (interior including nose), Hounshell is too much of an unknown, although his work ethic is what you want. Day is socially, work ethic, and team work-wise what you want, and except for some stunning lacks of judgment (Pitt) and the fact that he is a Junior, he is the man. He may be another that could benefit from a year of concentrating on improving his craft.
As far as the rest of the defensive linemen they are either too young or need to work on the level of their game, at this point, in my opinion.
DE - Ishaq would be a possibility if he is able to raise his game to his potential level. IF.
Corners - Do you off-task KR from developing into one of the best corners in the nation? Which I believe he can do. And he is a junior. I believe he is the kind of natural vocal leader that is the guy you want backing your captain. And not this year the captain himself. This would help with last year's problem, which appeared to be thin leadership after the captains, themselves.
Everyone else at corner is too inexperienced and or too young, except Cody Riggs. I feel as if he would be a great choice if he had come up in the program, but picking him would send mixed signals.
Safety. WOW. The only guy that appears to be taking over is Max, and again he is too young, and in the middle of growing into the position. Collinsworth? He has the work ethic and the experience, but what about play time this year?
This is a perfect year to make a special team statement, and honor a guy who has done a remarkable amount for the program in his four years. Brindza deserves it, is a good candidate, and maybe putting him there makes an important statement for the team this year.
On offense, many think Golson and Daniels are out with their violations. I don't know. I don't care. Let's see!
Nick Martin is almost being elevated to captain by Brian Kelly. Brian gave him the "Zack Martin Mantle" as clearly in the press conference as if he had a coronation ceremony during the PC.
Next choice on offense, Cam, Christian, and Ben in that order. CBreezy is an outside possibility, because of the special regard the coaches have been holding his effort, but that is all. Other upper classmen such as Hanratty, Hegarty and others just haven't established themselves as starters, and with the underclassmen coming in, who knows? Maybe ND will put an offensive lineman in the NFL that wasn't a clear starter at ND. Possible; in fact more possible than any lineman becoming a captain, other than Nick Martin in the next two years, IMO.
(*Making me unique on this site. EDIT : I know!)
