B1G position rankings: QB (units)

On Monday, we ranked the top individual quarterbacks in the Big Ten heading into the 2012 season. As we'll do with every group, we now take a look at the quarterback units as a whole throughout the league.

Having a good starter is critical here, but depth also matters. Quarterbacks can take a beating during the course of a season, so teams without experienced backups will fall a notch in these rankings. Away we go:

1. Purdue: Do the Boilermakers have one of the top quarterbacks in the league? No. But they have something no other Big Ten team can claim: three players with significant starting experience. The benefit of dealing with injuries the past couple of years is that now Caleb TerBush, Robert Marve and Rob Henry are all seasoned veterans who can be interchanged by head coach Danny Hope. That gives Purdue the best quarterback depth in the Big Ten.

2. Michigan: The Wolverines have the league's most experienced quarterback in star Denard Robinson. They also know that if something happens to Shoelace -- or if they just want a change of pace -- Devin Gardner can fill in capably. Redshirt freshman Russell Bellomy is more of a pocket passer who showed some things this spring.

3. Nebraska: We know all about Taylor Martinez. The question is, how good is Brion Carnes, his backup? That's hard to say, since Carnes hasn't played much, but he is entering his second season as the No. 2. Redshirt freshmen Tyson Broekemeier and Bronson Marsh and true freshmen Tommy Armstrong add depth if not experience.

4. Iowa: The Hawkeyes are ranked here mainly on the strength of James Vandenberg, who's reliable and durable. Things drop off after him, with senior John Wienke and redshirt freshman Jake Rudock the likely backup plans. Junior college transfer Cody Sokol is expected to redshirt, though that could change in case of emergency.

5. Ohio State: Braxton Miller should be one of the top quarterbacks in the league for the next three years. But what if he gets hurt, which seems like a real possibility as much as he runs the ball? Urban Meyer said Kenny Guiton showed marked improvement this spring. True freshman Cardale Jones was highly regarded on the recruiting trail.

6. Minnesota: While senior MarQueis Gray is the clear starter, sophomore Max Shortell gained valuable experience last year in key spots. And the Gophers are excited about the future with true freshman Philip Nelson, who was a major recruiting coup.

7. Illinois: Reilly O'Toole saw a lot of action as a true freshman and will continue to push Nathan Scheelhaase for playing time. Junior Miles Osei could serve as third-string QB.

8. Wisconsin: There's a reason the Badgers brought in another graduate transfer. This spring, Wisconsin had only two healthy quarterbacks -- Joe Brennan and Joel Stave, the latter of whom pushed ahead in the competition. Danny O'Brien should solidify the position, but with injuries to Curt Phillips, Jon Budmayr and Bart Houston, depth is still a concern.

9. Northwestern: Much depends on how Kain Colter improves as a passer. Sophomore Trevor Siemian completed 16 of 26 attempts last year and could give the Wildcats a different look if they want to move Colter around.

10. Michigan State: The Spartans got a preview this spring at what might happen if Andrew Maxwell gets hurt. Freshman Connor Cook had to lead both offenses in the spring game, as depth is a pressing issue here. Maxwell should be very good, but Michigan State still enters the season without a quarterback who's ever played significant downs.

11. Indiana: Tre Roberson had a promising rookie campaign yet felt some stiff competition this spring from junior college transfer Cameron Coffman. The Hoosiers will bring in promising prospect Nate Sudfeld, too. So even with two former starters -- Dusty Kiel and Ed Wright-Baker -- transferring in the offseason, Indiana should have decent depth here.

12. Penn State: Call me an optimist, but I believe Matt McGloin will be more effective at quarterback now that he's got a more modern offensive system and peace of mind that he's the starter. Still, the Nittany Lions have earned the bottom spot in these rankings with poor performance at the position over the past couple of years. Rob Bolden has not capitalized on his opportunities, and fan favorite Paul Jones has not played a down in college. At least Penn State has nowhere to go but up.