The identity of the 2013 Notre Dame offense instantly changed in drastic fashion when former starting quarterback Everett Golson was dismissed from the university for academic misconduct.
Both Golson and current starting quarterback Tommy Rees bring a unique skill set to the table, though each causes the Irish offense to operate in a different manner.
The challenge for Notre Dame head coach Brian Kelly is transitioning from a Golson-led offense to a Rees-led offense.
Through the first two games of this season, that transition has gone smoothly.
But with Rees set to see his eligibility clock expire following the current season and Golson slated to return to Notre Dame, Kelly will face yet another transition entering the 2014 season.
Comparing these two offenses has been a common point of discussion during the past calendar year, and it continues here.
When Kelly was hired at Notre Dame, he brought with him the reputation of being an architect of uptempo, high-scoring offenses.
The fourth-year head coach wants his offense to push the pace and dictate tempo in an effort to catch opposing defenses out of sync and position. Doing so allows the Irish offense to quickly move the ball down the field and consistently put points on the scoreboard.
However, the tempo with Rees taking the snaps varies tremendously from an offense with Golson leading the way.
Kelly spoke about Rees' strengths regarding tempo during his weekly press conference on Tuesday (via IrishIllustrated.com):
"Where (Rees) is going to make up for (not being a run threat) is getting us in the right plays," Kelly said. So our tempo is get to the line of scrimmage, give us enough time to get into the right plays. Let's give him enough time on the clock where we can get into some good checks."
As Kelly alluded to, Rees won't move the offense at the same rate Golson could because of his lack of mobility, but the offense is certainly more efficient with Rees because of his ability to make the proper adjustments on the fly.
The first and most crucial lesson to learn about Golson, the Irish's starting quarterback during the 2012 season, is that Kelly and the offensive coaching staff made every possible attempt to mask deficiencies in his mental grasp of the various schemes.
But what the Myrtle Beach, S.C., native provided that Rees couldn't is the ability to run the read-option—a major wrinkle that added layers of versatility to the offense.
Kelly's comments about Rees' limited physical abilities in the offense indirectly highlighted Golson's skill set (via IrishIllustrated.com):
"I think with the personnel that we have and the quarterback we have, we are not a team that really can run a lot of the read-option," Kelly said. "A lot of the stuff that's meant for real fast tempo, you need a quarterback that is going to be a run threat as well."
Because of Golson's speed, the Irish were able to quickly move the ball down the field through a mix of designed Golson rushes and simple routes across the middle of the field and in the flats.
Those possessions didn't produce nearly as many points as Kelly would have liked, though—particularly with the offense's struggles in the red zone.
While Rees isn't the mobile threat Golson is, he's a pure pocket passer capable of making all the throws the Irish offense calls for.
Combined with his mastery of the offense, Rees' presence on the field allows for a balance that the majority of coaches across the country strive for.
Let's take the Irish's 28-6 victory over Temple, for example.
Leading for all 60 minutes of action against the Owls, the Irish offense wasn't forced to emphasize the passing game like it did while trailing Michigan on Saturday.
Because Notre Dame's offensive line dominated the line of scrimmage, the Irish rushing attack plowed its way to 188 yards on the afternoon, effectively opening up the passing game.
The end result was Rees completing 16 of 23 passing attempts for 346 yards and three touchdowns. That's an outstanding 21.6 yards per completion.
The ultimate challenge for Rees is responding to defenses loading the box and flooding the backfield in an effort to rattle him. If he can make defenses pay for gambling, scoring opportunities will present themselves more frequently.
As I've stated, Golson, despite possessing a strong arm, struggles to read defenses. This results in a high number of incomplete passes and stalled drives.
The offensive coaching staff attempted to offset that weakness of Golson's game by emphasizing the running game with more two- and three-tight-end sets.
But when the Irish failed to establish the run last season—against Purdue (52 yards), Michigan (94 yards) and Alabama (32 yards), specifically—the end results were two nerve-racking victories and a humbling loss in the BCS National Championship Game.
Thus, should Golson return to Notre Dame, the hope would be that he's a more polished passer with a broader grasp of Kelly's offense.
Comparing Rees and Golson isn't comparing apples to oranges. In fact, it's more like comparing apples to Froot Loops.
Both players bring such varying strengths to the table that the Irish offense takes on an entirely different identity with each quarterback.
Yet Rees and Golson each have their weaknesses, showing that neither player is an ideal fit for Kelly's offense. Where Rees struggles with a lack of athleticism, Golson struggles with the mental aspects of the game.
A blend of the two would produce a headline-grabbing, potential Heisman candidate, but no such thing is possible.
For Rees supporters and detractors alike, the current season is the last you'll see of the 6'2", 215-pound quarterback at Notre Dame.
At that point, the phrase "a lack of mobility" won't have to be uttered or written again.