TAMPA — The Bucs have two key players sidelined with concussions, one for more than three weeks now, so players don't even need to look across the field on Sunday for a reminder of the shadow cast by concussions on the game they love to play.Yet, at the very intersection of football's physical nature and its growing concern about concussions and their impact on long-term player health is Carolina linebacker Luke Kuechly. The former NFL Defensive Player of the Year is dealing with his third concussion in as many years."It's terrible. It's horrible for any player," Bucs coach Dirk Koetter said Thursday. "I've said many times it's the worst part of this game — injuries in general, and concussions at the top of the list."Kuechly is 26, and didn't miss a game his first three NFL seasons. He quickly established himself as a tackling machine, with 463 in those first three years. In each year since, he's suffered a concussion and an extended absence — three games in 2015, then six to close out last season.Last year's concussion came on a Thursday night with a national TV audience, and showed a frightening moment with Kuechly crying on the field as trainers were attending to him. The uncertainty in his face — was this another concussion, and what would that mean for his career — is something all players can relate to."At some point, it's inevitable. It is a contact sport," said Bucs tight end Luke Stocker, who missed two games in 2014 with a concussion. "You can't water it down that much. I do think we've made progress since I've been here. There's definitely a lot of shots that you don't see guys taking, and you don't see guys playing through concussions or playing with symptoms. Guys are more aware of what possibly could come down the line for them. Guys are smarter about it."Bucs receiver Adam Humphries missed a game in December after a concussion, his first. He said some positions afford players a better chance to avoid head-on collisions that put them at risk for concussion."For a guy like Kuechly, who's gone through it multiple times at a position that's hitting every single play, it's tough," Humphries said. "You hate to see guys go through that. When your ankle is hurting, it's your brain telling your ankle 'I can't go.' When your brain is hurt, what's telling my brain if I'm ready to go or not? It's a tough decision to know if you're ready to go, but they do a great job."Players take comfort in the league's concussion protocol, which requires a series of steps before a player is cleared to return to a game. Among them:? If a player is diagnosed with a concussion during a game, he cannot return to that game;? A player must be able to practice fully without any symptoms after the fact;? A player must be cleared by an independent doctor to be released from the protocol.The NFL has spotters at all games looking for potential concussions and pulling players off the field when one is suspected. Bucs corner Robert McClain was taken off after a helmet-to-helmet hit late in Sunday's loss at Buffalo.He has been in protocol and hasn't practiced since.Bucs special-teams captain Josh Robinson has missed the last two games while recovering from a concussion suffered against the Patriots and will miss Sunday's game unless he's cleared. Robinson and McClain could not be interviewed for this story due to an NFL policy regarding players while they are in protocol.Bucs backup quarterback Ryan Fitzpatrick has been in the league since 2005 and hasn't had a concussion, but he's been checked during games, and takes comfort in the protection of those policies and having someone independent clearing players to return to playing."During the game, it's frustrating if you know you're OK for them to have to sit and test you, but at the end of the day, you understand why they're doing it," Fitzpatrick said. "Knowing what the risks are, we all still want to do it. I think the awareness, how far we've come even in the last five years, has been awesome."It's natural for players to want to push themselves back from injury, to play through pain to help their team, but a shoulder or an ankle is one thing; your brain is another."Seeing (Kuechly) going through that is tough," said Bucs guard Kevin Pamphile, who missed two games last year with a concussion. "Me personally, I wouldn't be mad if he wanted to sit down. At the same time, if he feels ready. A knee, an elbow, you can strengthen up, but the brain, that's tough to work on."Even once a player is cleared to return, playing with a history of concussions is another concern, one Kuechly is now dealing with again. He has returned to practice this week, but no decision has been made on whether he can or will play Sunday against the Bucs in Tampa. "The hard part with it is you have to understand what's going on with the guy," Panthers coach Ron Rivera said. "He plays hard. He plays reckless. The fortunate thing for the one he had this past week is it's not comparable to the ones he's had in the past. Again, I listen to what the doctor says and what the young man has to say and we go from there. At the end of the day, you want to make sure the guy is healthy."Koetter said he likes the way the league's protocol takes the biggest decision away from both the player and the coach, making safety a priority both during games and as players try to return after extended absences."I think the concussion protocol that they have in place right now is a huge help for everybody — for the players, for the doctors, for the trainers, for the coaches," he said. "I think it was a very smart move and I think it's serving a positive purpose."Contact Greg Auman at email@example.com and (813) 310-2690. Follow @gregauman.