Melvin Gordon hardly knew what to do with himself on the sideline in Arizona.

The rookie running back hadn't missed a game since 2012 -- but he was sidelined with an ankle injury against the Cardinals.

"It was tough going out there and watching everybody get better, getting prepared for the regular season, and me just sitting there chillin' on the sidelines (against Arizona) writing down the plays," Gordon told ESPN's Eric D. Williams. "So I tried to get my best out of it. I tried to stay in the game."

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Gordon found solace in the offensive playbook. He followed around his coaches, charted each Chargers' playcall, and took mental reps as others executed it on the field.

No experience can substitute for game experience, though. Gordon wants to do more than watch when his team plays Seattle in their third preseason game.

"Seattle's a good team," he said. "This will definitely be a challenge for me and my teammates to see where we're at. The more reps, the better -- it will help us and help me get ready for Detroit."

(h/t ESPN)