Now Keisel finds himself in the role of the bearded sage at the position with Hood and Heyward vying to replace Smith -- and the crater-sized vacuum of leadership and skill he leaves behind. Hood has the inside track, having seen significant starting time in the past two seasons in place of the oft-injured Smith. Keisel believes Hood is ready.
"Ziggy's been fortunate because since the day he got here he's been basically forced into playing," Keisel said. "When Aaron went down his rookie year, he had to come in and play right away so he has those mental reps, those physical reps, those game reps that you can't get any other way.
"You can go out here and practice all you want, but until you take it out and do it at game speed -- it's a whole other level. Luckily for him, he's been doing that now for three years, so stepping into this role as the starter from the get-go I don't think will be a big transition at all for him."
An affable West Texan with an 'aw-shucks' Amarillo twang, Hood embraces the challenge.
"Every guy wants the opportunity to start," he said. "What better chance than to get my opportunity right now? I've been working hard all offseason. I had a great offseason. I stayed around here. No need to go home. Pretty much just family and football for me.
"Now all you can focus on is the small things -- taking the right step, hand placement, getting your hips by -- all the little things that make you a better player.
"I feel ready. I've never been a vocal leader, but I try to do my best to lead by example," he said, a point that hasn't been lost on Heyward, who called Hood an "animal" in the weight room.
"All we do is just attack it hard," Hood said.
"If we're going to get up early and spend our time in the weight room, we might as well enjoy it and get big. There's no point in coming early and not doing anything, so you might as well just enjoy it and have fun with it."
Heyward downplayed that idea, or even a discussion of an increased role in the defense.
"I haven't even worried about that, I'm just trying to get better out here. I'll let my play show it off and continue to improve," he said, adding that he was simply glad to be taking advantage of his first OTAs (last year's were canceled because of league labor strife).
"I think it's vital. For me to take in the playbook a lot more and learn from my mistakes and take time to shine up and oil up and learn my technique and get better at it ... I'm not a senior guy at all. I have a lot to learn from Keisel and [Casey Hampton]. They'll bring me along, and Zig, if he's put in charge, he'll take care of us."
Keisel is bullish on Heyward's ability and knows that sooner or later, he'll be succeeded by him.
"I believe in him, I do. I feel like he's the type of guy that has the type of character that's going to come in and keep the ship rolling in the right direction," Keisel said. "I have all the confidence in the world in Cam, and when the day comes when I hang up the old No. 99, he'll do a great job.