In the sport of college football, each position is important. Not equally so, but close enough to one another that a single shaky beam along the frame could topple the whole structure.
If forced to choose, I guess I would contend that the defense is the most important unit on the field, the offensive line is the most important position group and the quarterback is the most important singular player. These contentions can be argued, though, and argued rather well. Because every member of the starting lineup plays such a vital role, almost any could be rightfully considered most important.
However, even a team with capable players at every on-field position would be moot without the guidance of a good head coach, and even a team without capable players at each on-field position might become relevant if it does have a good head coach. We've seen both of these things happen with semi-regularity—far too often to ignore.
In the sport of college football, each position is important.
Head coach just more so than the others.
For the sake of this argument, let's ignore the role head coaches play in recruiting. Yes, the players wouldn't exist (in the context of a given team) without the coaching staff's effort to secure them, so it would be easy to argue that coaches are responsible for the talent they coach in the first place. Same goes with the argument of player development—let's ignore it, at least for the time being.
Even once the season begins, on the sideline each Saturday in the fall, the head coach is the ultimate difference-maker.
If any other position compares, it is likely the quarterback, who is tasked with the most cerebral on-field job of any player in football.
But even he under center is often a function of his coach and the scheme he is placed in. For an example of this, look no further than some of last year's conference champions.
Auburn won the SEC with a converted defensive back from Georgia (by way of JUCO), Michigan State won the Big Ten with a guy who lost a QB battle with Andrew Maxwell—Andrew Maxwell!—and Stanford won the Pac-12 despite an up-and-down year from Kevin Hogan.
In each of these cases, the QB was set up for success by the efficiency of the rest of the team, and the efficiency of the rest of the team was created by the preparation/management of the coach.
Which shouldn't serve to devalue the role of the players themselves.
A team with modest players and a great coach has a chance at exceeding expectations, but it isn't guaranteed (e.g. Boise State 2013).
Still, that it can rightfully expect to compete against any team in the country (e.g. Boise State 2006-12) proves coaching is the sport's greatest and most powerful equalizer.
When we speak flatteringly of quarterbacks, we oftentimes refer to them as on-field "extensions of their head coach." This is intended and taken as a compliment, especially if the head coach is a good one.
But now consider the opposite: a head coach who is referred to as a sideline "extension of his quarterback." No matter how skilled the QB, this in no way seems like a pat on the back. It seems like he's somehow being patronized, being told that he's not in control.
The coach is the glue that holds each unit together. He's the reason a team like Alabama, for example, can engage on a wild, open, six-man quarterback competition this spring and fall without dropping out of most publications' preseason top-five rankings. Losing AJ McCarron will hurt, sure, but the Crimson Tide will find a way to recover.
They still have Nick Saban at the helm.
Imagine if it were the other way around: if Saban had left for the NFL and McCarron had remained in Tuscaloosa. Would anyone be quite so confident? People could (and, I contend, would) be more inclined to look for the holes in a team that no longer had its future Hall of Fame head coach, and they wouldn't necessarily be wrong for doing so.
The best teams have a delicate balance of coaching and players, of scheme matched with quarterback, playmakers, defense and special teams. This will always be the formula for success in college or any other level of football, and ideally a team would not have to choose between any of those options. If it did, however, the choice would not be a difficult one. At least for a smart team, it wouldn't.
The coaching should always come first.