He's not "the" leader as that goes to SDH in my mind but Evans is definitely up there!
No disrespect to SDH at all, as there are different types of leaders. SDH does a great job and I'd say is the captain of the D, always making sure guys are lined up right, making adjustments etc. In that regard he's a great leader.
Then there's the leadership that sets the tone of play with an attitude that we're going to downright physically dominate the other team and setting a standard others want to match. That's the alpha-dog mentality Saban talks about. In that regard Evans is clearly the man. Harrison is close, and Buggs is starting to emerge and likely would be one if he'd been a full time starter all year.
last year one of the alpha's was also the captain in Foster, but the other two alpha's, Anderson and Allen, were just as, if not more, important in setting that 'spiteful' tone that's our trademark.