Defensive line

	Many experts downgraded Mike Patterson because of his lack of height. Jamie Squire/Getty Images

Overrated: Erasmus James, Wisconsin
Admittedly, James was the most dominant pass rusher in the country the first half of last season, including a clinic against Purdue in which the Boilers wound up using their running back as an extra blocker just to try and slow him down. But the four, injury-riddled years before that, James was at best an average player, and after sustaining an ankle injury in that Purdue game, he was largely a non-factor the rest of the way, particularly in the Outback Bowl against Georgia. Certainly he's shown the potential to be an elite player, which is why he remains so high on so many draft boards, but it's generally dangerous to bank on players who have had such small windows of brilliance. They can just as easily become flashes in the pan.

Underrated: Mike Patterson, USC
Besides Matt Leinart, Patterson, even more so than fellow defensive tackle Shaun Cody, was the single most important piece of the Trojans' consecutive national title teams. Trojans head coach Pete Carroll raved on numerous occasions of Patterson's unique ability to disrupt opposing offenses by exploding into the backfield to make one big play after another. Imagine my surprise, then, when I loaded up Don Banks' most recent first-round projection and saw Oklahoma tackle Jammal Brown -- whom Patterson bulldozed in the Orange Bowl -- but no Patterson. The reason, of course, is that he's undersized -- just shy of 6 feet, three inches shorter than most prospects at his position. But what he lacks in height, he makes up for both in width (292 pounds, about the same as top-ranked tackle Travis Johnson) and unmatched quickness, and I find it hard to believe a guy who was so dominant at such a high level in college won't become at least a reliable starter at the next level, one worthy of a first-round pick.

Linebacker

Overrated: Channing Crowder, Florida
It's not that Crowder isn't an exceptional talent. He most definitely is. It's just that he's way too immature as of now to make the jump to the NFL. Crowder was technically a true sophomore last year -- he took a year off after high school to rehabilitate a knee injury -- and even then, he only played in nine games due to injuries and a one-game suspension. So, we're basically talking about a 21-year-old guy in whom some team is going to invest several million dollars based on one outstanding freshman season (106 tackles) and parts of another (73). Not to mention he was something of a loose cannon throughout his time in Gainesville, getting arrested twice outside the same nightclub. Hey, I suppose it works for the NBA.

Underrated: Lofa Tatupu, USC
Just like Patterson, Tatupu was an indispensable figure in the Trojans' recent success, particularly last season, when he led the team in tackles (104), intercepted three passes and forced three fumbles. He makes plays, often game-changing ones, all over the field. Scouts, however, are likely fixated on his height (just under 6 feet) and lack of natural athleticism. He is, after all, a classic overachiever who began his college career in obscurity at I-AA Maine. But there's no denying Tatupu's impeachable instincts and playmaking abilities, not to mention NFL genes (his father, Mosi, played for 14 seasons). Linebacker would seem to be the one position where all those things would be particularly beneficial.

Defensive back

Overrated: Fabian Washington, Nebraska
Every year there's that one "workout wonder" who manages to drive up his draft stock solely because of his 40 time. Washington is that guy this year, having dazzled league types with his blazing 4.29 burst at the combine, best of the event. Kudos to him. Washington had his moments at Nebraska, but he was hardly what you would call a lock-down cover guy. In fact, teams managed to pass for 268 yards per game against the Huskers last year -- eighth-worst nationally -- despite the presence of Washington and similarly touted DB Josh Bullocks. And scouts openly acknowledge that Washington is weak in run support. So basically, he's a first-round pick because he can run fast. I didn't realize the NFL had added a halftime track-meet to its games.

Underrated: Ernest Shazor, Michigan
The same factor, speed -- in this case a subpar, 4.7 40 -- is what's dragging down Shazor's stock. Never mind that, as a junior last season, he was without question the most disruptive player on the Wolverines' defense, making a team-high 84 tackles, 10 tackles for loss and forcing and recovering two fumbles. His punishing hit and accompanying strip of Purdue receiver Dorian Bryant in the final minutes preserved a 16-14 road win over the Boilermakers. An incredible athlete with ideal stature (6-4, 228), Shazor is being pegged as a second-round pick at best. Personally, with the exception of Georgia's Thomas Davis, who has future All-Pro written all over him, I'd take Shazor over any other safety.

Stewart Mandel covers college sports for SI.com.