The Bears first-round pick was a linebacker in high school (as well as a running back, kicker, punter and punt returner). When he got to Boise State, he became a defensive end.
The next year, McClellin moved between defensive end and outside linebacker, depending on the opponent and the game plan. He also played some inside linebacker.
In 2011, Boise State defensive coordinator Pete Kwiatkowski got even more ambitious with McClellin, playing him at end, outside linebacker, inside linebacker and as a hybrid outside linebacker-safety.
"Besides being a good athlete, he understands concepts," Kwiatkowski said. "He studies the game. He can handle things and play fast."
Lost in the debate over McClellin's best NFL position is that he could succeed at either defensive end or outside linebacker because of his outstanding versatility.
Under the direction of someone like Jets coach Rex Ryan, McClellin probably would be asked to play almost every instrument in the defensive orchestra.
But for Bears coach Lovie Smith, McClellin is going to play defensive end, and only defensive end.
"You won't come to practice and see him working on pass coverage," Smith said. "You will see him hitting the bag and trying to improve his technique at getting to the quarterback."
The way the Bears look at it, McClellin's best trait is also the most valuable commodity: Rushing the passer. So why have him do anything else?
"You can find any big guy who can drop to a spot in coverage," Smith said. "There are very few guys who can rush on the outside."
Really, McClellin has been more of a defensive end than anything up to now.
Kwiatkowski said McClellin mostly played with his hand on the ground and estimates he rushed up to 65 percent of the time, almost 100 percent on passing downs.
"We liked to be in a four-man front and have him rush (as a end)," Kwiatkowski said. "He is very instinctual leveraging blocks and finding the ball."
The Bears studied 270 of his pass rushes as a defensive end and outside linebacker and concluded he was best as a defensive end.
McClellin might be solely a defensive end for now, but he could be more in the future. If the Bears ever transition to a 3-4 defense, or a hybrid 3-4, he's a perfect player to build around.
McClellin even could have a future at middle linebacker. Two front-office men thought McClellin could develop into Brian Urlacher's eventual replacement. At 6 foot 3, 260 pounds, he is built more like Urlacher (6-4, 258 when he came to the NFL) than Julius Peppers (6-6, 283).
McClellin ran a 4.62 in the 40-yard dash. Urlacher ran a 4.58. It's interesting that both players were used as a linebacker-safety hybrid in college.
For McClellin in the middle to be a possibility, he probably would have to struggle at defensive end though.
"He has potential (at middle linebacker)," Kwiatkowski said. "He did some things that were natural, dealing with blockers, finding the ball. He was not out of position very often."
Smith said as far as he is concerned, McClellin playing middle linebacker "is not even a conversation."
Smith saw tape of McClellin at all his positions. But the only thing he derived from it is McClellin has the type of athleticism he is looking for in an end.
"The things he did in college, that's great as far as being able to see his athletic ability," Smith said. "Besides that, there is no interest to us.
"We were looking for an athlete. Look at who is on the other side of the ball as far as quarterbacks. They are big athletes. Look at Aaron Rodgers, Cam Newton, Robert Griffin III, the skill set of the new breed of quarterback. You need those types of athletes rushing to keep them pinned in."
No matter where he lines up, McClellin should have a long NFL career making quarterbacks uncomfortable.