SAN JOSE, Calif. (AP) Luke Kuechly strolls happily through the Carolina Panthers locker room smiling and addressing teammates as he passes.
He stops at defensive tackle Dwan Edwards' locker first and shares a laugh before moving up the carpeted, rectangular room and sitting with a group of running backs to chat.
He talks. He laughs. He leaves people in a better mood as he departs.
The Panthers seem to agree that Kuechly is, as safety Roman Harper describes him, ''the nicest guy I've ever met in the world.''
''Definitely,'' adds Edwards.
But they also know about Kuechly's ''other side'' - the moment when the All-Pro linebacker steps on the football field, things change quickly.
''He has this alter ego he manages to control. In the locker room he's so jolly, like, `Hi Cameron,''' said quarterback Cam Newton, raising the pitch in his voice at the end to simulate Kuechly's cheery voice.
''And then on the field he's like `Arrrrgh!''' Newton said, his voice turning more intense.
The QB shakes his head, ''It's crazy.''
''On the field he turns into something else - like Captain America saving everybody and everything,'' cornerback Josh Norman said. ''He has a switch. Some players got it and some players don't - he definitely has one.''
Whatever switch Kuechly has, it certainly works.
He has more tackles than any player in the league since being selected by the Panthers in the first round out of Boston College in 2012. He has more interceptions (11) than any linebacker during that span and was named NFL Defensive Player of the Year in 2013.
The Panthers are 44-24-1 since his arrival and will play in the Super Bowl on Sunday against the Denver Broncos.
Coach Ron Rivera said he sometimes has to remind himself that Kuechly is only 24.
''What more could you ask for than a guy to come in and take the league by storm?'' tight end Greg Olsen said. ''There is that expectation of what more can he do year-in and year-out? He seems to top himself. He's a special player.''
''He's my favorite football player ever,'' said running back Jonathan Stewart.
The humble Kuechly gets bashful, almost embarrassed, talking about himself - particularly when it comes to his fiery demeanor on the field.
The 6-foot-3, 240-pound Kuechly says he lives by the simple motto of treating other people the way you want to be treated, but acknowledges that kind of goes out the window on game day.
''You can be one guy off the field, but when you get on the field the competitive aspect of who you are takes over,'' Kuechly said. ''It doesn't matter who it is, everyone wants to compete, everyone wants to win and you have to do your best because if you let up for one second something bad will happen to you.''
Broncos tight end Owen Daniels calls Kuechly ''an animal'' on the football field.
''He's sideline-to-sideline, flying around, passing guys, his own teammates, to make tackles,'' Daniels said. ''You see all that stuff on film and it's really impressive.''
Then he laughs and says, ''Good to know he's a nice guy off the field.''
Kuechly has 19 tackles, three pass breakups and two interception returns for touchdowns already this postseason.
Newton never misses a chance to playfully poke a little fun at Kuechly's humble, nice-guy persona. He was the one that dubbed the seemingly too-good-to-be-true Kuechly ''Captain America,'' in part, to pick on him.
But when the teasing ends, he wants Kuechly on his team.
''Being around Luke makes me better,'' Newton said. ''I haven't been around a lot of people that I can say their preparation, their play, their skillset brings the best out of me. When I see Luke and the work that he puts in from working out to preparing in the classroom and for it to come out on the field, it makes a person like me want to be better.''
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