There was a time when Bobby Petrino's offense was described as a power-spread. His balance of passing from single-back formations with diverse run games allowed his offenses to run down opponents' throats or spread to throw with traditional pro-style quarterbacks.

Petrino's Louisville opens 2015 in an interesting situation with dual-threat QB Reggie Bonnafon, the current favorite to start. Instead of having a QB who just needs to be taught how to wield the Petrino system, Louisville has a player with the ability to help the offense reach its highest potential.

In Week 1, the Cards face the Auburn Tigers (Sept. 5 at 3:30 p.m. ET, CBS), who are in a similar situation. While Gus Malzahn has won with a variety of quarterbacks, he's enjoyed his greatest success with dual threats like Cam Newton and Nick Marshall.

With Marshall moving on, the Tigers turn to junior Jeremy Johnson, who's no slouch but is better defined by his strong arm and passing abilities than his running.

In the Auburn power-spread, which is less pro-style than Petrino's, the QB has to execute option concepts to prevent teams from ganging up on the run. With the QB's legs no longer a main constraint on the defense, run/pass option plays will be elevated.

If either team isn't able to establish its new identity in fall practices, that team could very well open with a loss in Atlanta.

The new edition of the Auburn offense

Offenses and defenses both have 11 players. But in most offenses, the quarterback is a distributor, not a potential threat, essentially making it an 11-on-10 advantage for the defense. The spread-to-run philosophy is dependent on the quarterback being able to control that extra player, the one the defense can bring into the box to outnumber the run.

When Auburn got ahold of the 6'5, 245-pound Newton, it did this with the power-read play, which featured the massive QB on traditional power runs and controlled the edge of the defense with a sweep option.

When the smaller Marshall took over, Auburn featured a new take on zone read, in which Marshall had a lead blocker around the edge. Both plays were massive hits and are now standard across the nation.

But Johnson isn't as quick around the edge as Marshall nor as powerful as Newton. What he does offer is an ability to attack outside with his arm:

Johnson's ability to make quick reads and throw outside on run/pass options will be critical in attempting to run on Louisville's fronts. In the Georgia Dome, the Tigers will face a lot of alignments like this one by Todd Grantham's defense:

The Cardinals have a lot of turnover on the back end of their defense, with all four starters departing. But they return nickel Jermaine Reve and welcome transfers in CB Shaq Wiggins and SS Josh Harvey-Clemons, who learned Grantham's scheme at Georgia.

For the Tigers, the challenge is this Cover 4 coverage that is very popular these days and could be especially potent with the Cardinal personnel. The design asks the boundary corner (left corner, above) to be responsible for vertical routes, freeing the strong safety ($) on the boundary to be a run-force defender. When that box safety is 6'5, 230-pound Harvey-Clemons, you're looking at a difficult day trying to run the football.

This is a problem Auburn struggled to answer in 2014, notably against Kansas State, as introducing the QB as a running threat doesn't necessarily equalize the numbers if the secondary is aggressive. The better way to attack is outside the hash marks and deep with the passing game.

Johnson can throw with anticipation on comeback routes. Auburn's hope would be to hit it big on a few of these and force Harvey-Clemons to play as a deep-half safety instead of a shallow box player.

This strategy depends on receivers being able to get separation to present a target and to do something with the ball in their hands, or else this won't be an efficient tactic to punish the Cardinals for outnumbering the run.

The highest ceiling will come if Johnson can throw with better anticipation over the middle to preseason All-SEC WR D'haquille Williams and on downfield run/pass options:

The goal with RPOs is to control the outside overhang defenders, who allow a defense to outnumber the running game. With a bubble screen to the broad (right, above) side of the field, the offense can keep the nickel (N) from crashing down on the run. A skinny post to the X receiver could punish an aggressive fill by the strong safety ($).

Johnson has to be able to know where to read before the snap and make a decision and accurate throw for these to work. If they do, the Auburn run will really get rolling and Tiger fans won't miss Marshall too badly.

Bonnafon and the Petrino way

When Petrino is running the ball, he's not interested in trying to control those overhang defenders with the threat of a pass option. He'd much rather just bowl them over with a blocker.

With RB Brandon Radcliff back, along with excellent blocking tight end Keith Towbridge, Louisville is going to look to establish the run from big formations against any and all comers.

Petrino likes to do this with plays like G-lead, a man/zone combination that zone blocks the backside (left, below) and blocks down on the strong side (right), pulling the guard around the corner to blow up the edge defender (E) and clear a lane for the back (R):

To supplement, he will also use Bonnafon as a runner on zone read plays from spread sets.

Ultimately, the home runs are going to come from his passing game, which Bonnafon struggled to execute in 2014. After fighting through the tragic loss of his father, Bonnafon turned a corner in this year's spring game, but he'll face a tough challenge in Will Muschamp's defense without first-round WR DeVante Parker.

In addition to Muschamp, the talented group adds former All-Big Ten cornerback Blake Countess and former high school Army All-American safety Tray Matthews, after he was kicked out of Georgia.

With all of this inherited talent, Muschamp is going to bring the pressure, in disguised ways that even veteran QBs could struggle to sniff out.

One response will be for Bonnafon to recognize it before the snap and get Louisville into a running play like G-lead. That will punish the blitz by flanking the defense with blockers. Another will be to understand where his hot reads are so he can get the ball out.

Petrino's system, especially his shallow cross concept, is designed to give the QB hot reads to beat the blitz, but the QB has to recognize the pressure and know where the ball should go. The freshman struggled with this in 2014, and Notre Dame's zone blitzing flummoxed him.

Who transitions better?

Auburn's system is more accommodating of Johnson's talent than Louisville's is of Bonnafon's. The ideal power-spread QB is a player who can hit home runs in the deep passing game, and Malzahn probably isn't too worried about giving up some QB runs in exchange for a more lethal passing game.

But in Petrino's system, Bonnafon's athletic ability is more of an also/and that can supplement the package, rather than emphasize a different facet.

Because of the greater distance Bonnafon has to travel to be a master of his system and the loss of security blanket Parker, look for Auburn to have the edge.