Before the 2011 NFL Scouting Combine happened, folks had Marcell Dareus going right around this range, outside of the top five picks, and the 49ers were considered one of the likely destinations for him. Fast forward to post-combine, and Dareus is being mocked as high as the first overall pick to the Carolina Panthers. It's definitely a possibility, Dareus is a monster who can play any position on the defensive line in any defense, but combines only tell so much of the story, and our own Ernie Pomin noted as much when he had the Denver Broncos taking Nick Fairley second overall.
Cornerback and outside linebacker are bigger needs for the 49ers, which is why they'd consider taking Prince Amukamara of Nebraska or Robert Quinn out of North Carolina here at seven, but drafting solely for need is never the best course of action. There are cases where you could say Amukamara is the best player available at seven, but not when Marcell Dareus is still on the board.
So they go with the 6'3'', 320 pound lineman out of Alabama. He absolutely blew up at the combine, running a 4.92 and generally just looking fantastic out there. Folks have suggested his ability to make a difference in the vein of Ndamukong Suh. In San Francisco's 3-4 defense, he'll line up right away at left defensive end, but don't discount nose tackle as a possibility. Nose tackle may not be the best fit, and he might not even want to play the position
(like that matters), as it is probably a big waste of explosive athleticism at this point. He'll replace Isaac Sopoaga and improve what is already a strength, and maybe someone like Manny Lawson, already on the roster, looks better rushing the passer with Dareus abusing offensive linemen in front of him.
It doesn't address one of the top three needs for the 49ers, but he's one of the best players in the draft and he makes the team better any way you look at it. New defensive coordinator Vic Fangio can design a myriad of ways to use Dareus in blitz formations with his aggressive, movement-oriented defense.