College freshmen aren't supposed to lead Top-25 football teams. That's supposed to be left to the upperclassmen; the guys with the most knowledge and the most experience.
And yet, just three weeks into the college football season there already are a few precocious underclassmen helping to march their team up the college football ladder.
Here are three freshmen that have keyed their team's ascent in the rankings.
Todd Gurley: Running Back, Georgia
Going into the 2012 college football season, it was assumed that a talented freshman running back would lead the Bulldogs' ground game to new heights. But that back wasn't expected to be Todd Gurley.
It was Keith Marshall (the No. 5 overall prospect according to ESPN) who was supposed to be starring in Georgia's backfield. Marshall has run the ball very well, gaining 182 yards on 32 attempts and chipping in a touchdown as well. But he's been nowhere near as good as Gurley.
Gurley has rushed for 296 yards on just 28 attempts. That's a staggering 9.9 yards per carry. He almost averages a first down every carry. Let that sink in.
As if things could get any better, Hurley has also scored five touchdowns this season, including a 100-yard kickoff return.
Georgia hasn't played a close game yet, but if Gurley keeps playing the way he has, it's hard to imagine that they ever will. He's been that good and that important to the Georgia offense.
Marcus Mariota: Quarterback, Oregon
Oregon was ranked No. 5 in the preseason polls, but the quarterback position was still a big question for the Ducks. No one knew whether a redshirt freshman like Mariota was ready to step into the shoes of predecessor Darron Thomas.
No one is questioning Mariota now. The young quarterback has led Oregon to a 3-0 record and a blistering average of 54 points per game. It is worth noting that Oregon hasn't been facing very tough competition, but Mariota still has been undeniably impressive.
He's thrown for 674 yards and eight touchdowns and completed more than 75 percent of his passes in the process. Mariota may have inherited a talented team, but if he performed poorly, he easily could have submarined the Ducks entire season.
Instead, he'll be competing for All-American teams, and maybe even for a national championship.
Brett Hundley: Quarterback, UCLA
Raise your hand if you honestly expected UCLA to be a top-20 team this year. No one? There's no shame in that. Not many people did.
The Bruins have been trapped in football mediocrity for what feels like forever, but thanks to redshirt freshman quarterback Brett Hundley, it looks like those days are over.
Hundley, a talented dual-threat quarterback, has led the Bruins to a perfect 3-0 record, including a big win over Nebraska (who were ranked No.16 at the time).
He's completed 67 percent of his passes for 827 yards and eight touchdowns to just three interceptions. He's also tacked on 119 yards and a touchdown on the ground.
Admittedly, Hundley has had a lot of help from running back Johnathan Franklin. Franklin leads the nation in rushing with over 180 yards per game and has been a huge factor in the UCLA offense.
But none of that should take away from what Hundley is doing. He is somehow playing like the best quarterback in a conference that includes USC's Matt Barkley, the assumed No. 1 pick in the NFL draft.
The Bruins couldn't have risen to No. 19 in the AP Poll without Hundley steering the ship, and he deserves recognition for his play so far.