Freshman running back Kenan Christon has been the storyline of the week for USC -- in part because of his 103-yard, 2-touchdown debut last Saturday and in part because of the Trojans' razor-thin depth chart at the position.

USC has no choice but to lean heavily on the impressive freshman this Friday night at Colorado and moving forward with Vavae Malepeai (knee surgery), Markese Stepp (ankle surgery) and Stephen Carr (hamstring strain) all unavailable.

It's wild to think that a week and a half ago Christon was No. 5 on the depth chart (also behind former walk-on Quincy Jountti, who fumbled on his first carry last Saturday).

Ordinarily, that might be cause for major concern for a team. It is a concern for USC from the aforementioned depth standpoint, but Christon's elite speed and upside actually make this a situation of substantial intrigue for the Trojans.

So we turn the film room spotlight on Christon's debut performance, breaking down each of his 8 carries and 103 yards in the second half vs. Arizona -- including his 55-yard and 30-yard touchdown sprints -- along with an evaluation of his strengths and weaknesses at this point.

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Result: 7-yard gain

Analysis: For his first carry of the night, Christon lines up to the right of QB Kedon Slovis in the pistol with TE Erik Krommenhoek serving as an H-back to the right. The Trojans have the numbers advantage at the line of scrimmage before the snap -- Arizona only leaves three down linemen to go with three linebackers. Christon takes the sweep going left and almost immediately notices the sliver of a hole opening between guard and tackle. In a heartbeat, he plants his foot and cuts upfield at full speed. The acceleration here is impresssive -- Christon is sprinting only a step after his cut. He carries the ball straight upfield through the lane before meeting a tackler and uses his momentum to grind forward to complete the gain of 7.

Result: No gain

Analysis: From the same formation, starting the next possession, Christon runs a slam play straight toward the middle. The Arizona penetration is there almost instantaneously, and the back manages to drive forward to the line of scrimmage after contact before being taken down for no gain. There was not much to do with this carry.

Result: 7-yard gain

Analysis: The Trojans once again line up in the same formation, except with Christon to the left this time. They run an inside zone to the right, and a gaping hole opens up for Christon. Christon cuts and hits the lane at full speed as always, but instead of angling for the open grass toward the sideline he chooses to run through a smaller gap between two Wildcats. He runs into one of the defenders and manages to fall forward after being thrown for a gain of 7. Had he kept this run to the outside, it might have broken for much bigger yardage.

Result: 1-yard gain on first-and-goal

Analysis. Set up 6 yards from the end zone, USC lines up in tight end trips to the right with Christon behind and to the left of Slovis. The call is once again for an inside run, but the Arizona front crashes hard, leaving the edge completely free. However, instead of cutting the run wide, Christon barrels straight ahead into the defense, picking up only a yard before going down. Once again, Christon misses out on an easy read; this one should have resulted in 6 if only he’d bounced the run wide.

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Result: 55-yard touchdown

Analysis: USC lines up in tight end dubs, and Christon is set behind and to the left of Slovis. The play is an inside zone run to the left, and it’s executed perfectly by the offensive line. Jalen McKenzie in particular does an excellent job, pulling all the way from his right guard position to the left edge to obliterate the Arizona defender keeping contain. His block blasts open the running lane, and this time there’s no confusion for the freshman running back. Christon plants his foot and shoots through the hole, and from the moment he does it’s clear that a big gain is on its way. There’s only green grass ahead of him for 10 yards and Christon turns on the jets. It’s instantly noticeable that no one else on the field has that kind of speed. Even though the deep safety in front of him has perfect position to make a tackle after about 15 yards, Christon angles his run slightly towards the sideline, and that tiny change of direction makes it impossible for the safety to reach him in time as he gallops into the endzone.