Oregon running back Byron Cardwell runs a drill during preseason football practice on Thursday in Eugene. Cardwell is vying for the No. 3 spot on the RB depth chart behind C.J. Verdell and Travis Dye.

EUGENE — The top of Oregon’s depth chart at running back is chiseled in stone, but the Nos. 3-5 spots are wide open.

With Sean Dollars recovering from an offseason leg injury, true freshmen Byron Cardwell and Seven McGee and second-year freshman Trey Benson are all vying for the opportunity.

Benson did not scrimmage with the Ducks on Saturday because he’s still recovering from major knee surgery, but he’s expecting to be back to full-go by the time the season begins.

“Those two young guys are kind of what we thought they were,” running backs coach Jim Mastro said. “It’s all about reps with them. Got to get them up to speed as fast as we can. Trey is almost back to 100%. Once he’s back to 100% it’ll be a good battle for that 3 spot right now. … This is the best depth we’ve had since I’ve been here. It’s a good problem to have.”

The additions of Cardwell and McGee radically change the outlook at the position even compared to the spring, when walk-ons Aaron Smith and Cross Patton got the most work in order to lessen the load on C.J. Verdell and Travis Dye.

Mastro said Verdell and Dye will see action on Saturday night, but the two freshmen will get the majority of the reps during the scrimmage, the first of two before the season.

“They certainly have the talent,” offensive coordinator Joe Moorhead said.

“We’ve got to give them some experience and reps in camp. I think if they’re provided the opportunity, based on how the season unfolds I have the utmost confidence in those young guys.”

Running back is a position that allows for true freshmen to see the field more quickly and easily compared to offensive or defensive linemen or quarterbacks.

Mastro said the aspects of the passing game, both as receivers and blockers, is where the trio of younger backs have the most to learn before being put in games, but their physical capabilities are not in question.

“Those guys are going to help right away, have elite talent,” Oregon coach Mario Cristobal said. “They’re physical, strong. You can push them. They already know that in our regimen they’re going to get pushed, challenged hard and strong. They’ve responded really well to that.

“Byron is a bigger guy now, 215 pounds just about, still growing. Seven is a lot bigger than you would think coming in so explosive and dynamic with the ball in his hands, not only out of the backfield but spread out as a wide receiver, special teams, those units also.”

The 5-foot-9, 181-pound McGee is the more agile, nimble runner while the 6-foot, 210-pound Cardwell is similar in stature to Benson and taller than Verdell.

“(Cardwell) still hasn’t figured out his body yet,” Mastro said.

“Once he does, it’s going to be endless for him.”