The skinny: There are a number of young players that will contribute to the Trojans' effort for a Pac-12 title in 2015, and Marshall's versatility will help him see the field right away. He's best suited to play safety, but likely will play as a nickel corner first while filling in quite nicely for the departed Nelson Agholor on kick returns. USC has utilized a number of freshmen as two-way players the past couple of years, and perhaps Marshall will join the club.

The skinny: The Canadian recruit will be, at minimum, a key rotational player on the interior right away, if not the starting replacement for the departed Jordan Phillips. The Sooners have plenty of key pieces returning on defense, but Gallimore's ability to make plays at defensive tackle will help significantly as the team tries to get back into title contention.

The skinny: Considered by many to be the No. 1 recruit in the country coming out of high school, Cowart will play a key part in coordinator Will Muschamp's retooling of the Tigers' defense. The team lacked a strong pass rush last season, and though he might not earn a starting job right away, Cowart should still be able to rush the quarterback and contribute in a number of situations that require him to get after offenses.

The skinny: The front seven for the Bulldogs is going through a number of changes and there will undoubtedly be a place for Thompson, who was the team's top recruit in its most recent class. Physically, he should be able to step in right away and play, and his ability to get upfield is matched by few at his position. He'll be a big weapon on third down for defensive coordinator Jeremy Pruitt.

The skinny: Derek Barnett came in as a true freshman last year for the Vols and exploded into a nearly unblockable player. Many around Rocky Top are hoping that McKenzie, the son of Raiders GM Reggie McKenzie, will do the same. Fellow freshman Shy Tuttle enrolled in the spring and has a bit of a head start on McKenzie, but there's little doubt McKenzie has the ability to come in and solidify the middle of the defense early on.

The skinny: Arik Armstead has departed for San Francisco, but the Ducks still have defensive lineman DeForest Buckner -- one of the top defensive talents in college football -- to build around in 2015. The team is hoping that Kaumatule, a five-star recruit from Buckner's high school in Hawaii, will be able to step in right away to fill Armstead's shoes as a similarly sized 6-foot-6, 290-pounder who can play multiple positions and roles.

The skinny: The Bulldogs lost some key starters from last year's squad and will be counting on the talented freshman to contribute right away. Dan Mullen hasn't typically relied heavily on true freshmen, but Peters will immediately be involved in the secondary and play a big role in rebuilding the team's defense in a difficult SEC West.

The skinny: James enrolled early for spring football, and left a lasting impression on his Seminoles teammates with his physical style and ability to make plays all over the field. He might not be the starter at safety, but he'll be a key figure in nickel and dime packages. James looks like the latest defensive back who will make his mark at FSU.

The skinny: Stanford has plenty of pieces to replace on defense this season, but it might be reloading instead of rebuilding thanks in part to players like Thomas. The jewel of the 2014 recruiting class, he redshirted last season, but is primed to be a key player for the team in 2015. Injuries slowed Thomas a bit during spring practices, but the Pac-12 will quickly get to know his name.

The skinny: Malachi Dupre came in as a true freshman last season and immediately became a playmaker. This year it will be Johnson's turn. Like Dupre, Johnson is a blue-chipper from New Orleans who should immediately be in the fold at receiver due to his terrific quickness and hands. There have been plenty of Odell Beckham, Jr., comparisons for Johnson, and while he might not live up to that hype, he'll help a young offense grow.

The skinny: Dalvin Cook is the unquestioned starter at running back for Florida State after a 1,000-yard season as a freshman last year, but no matter who replaces Jameis Winston at quarterback, the Seminoles will renew their efforts to establish the run in 2015. Patrick impressed during spring football, and he should already be the first option off the bench behind Cook when the team opens the season and can provide a nice change of pace.

The skinny: Amari Cooper is gone but not forgotten at Alabama. However, many around the program are expecting Ridley to immediately replace some of Cooper's production. Coordinator Lane Kiffin has had success with freshmen at the position before and should again with the talented Ridley.

The skinny: The blue-chipper will head to Austin with high expectations. Plenty of people are counting on him to live up to the early billing as the next great defender in Burnt Orange. He enrolled early and didn't look out of place during spring practices.

The skinny: Why is Ivey No. 2 on this list? Well, he's a five-star recruit, and the Gators have a serious need on the offensive line. The team is essentially starting from scratch up front with so many losses to graduation and the NFL draft. New head coach Jim McElwain will have his work cut out for him as a result. At least he can pencil in Ivey at some spot along the line, likely at right tackle.

The skinny: It would be beyond surprising if Rosen isn't selected to take over for Brett Hundley. The consensus top QB in the class of 2015, he enrolled this spring and positioned himself as the front-runner to be the new starting signal-caller. With a fairly loaded roster returning, his performance could be a deciding factor in whether or not the team makes a serious run at the Pac-12 title.