He didn't learn it as a true freshman, but rather as a high school player for Cleburne County in Heflin, where he amassed over 8,000 all-purpose yards.
"Being a running back in high school, running up the middle and hitting linebackers, it gives me an edge to be a physical athlete," Prothro said.
Ask Charlie Peprah, perhaps the most experienced defensive back. Peprah and Prothro have spirited one-on-one battles every day in pass drills, and Peprah will attest to Prothro's strength.
"He's physical," Peprah said. "He's more like a (former LSU receiver Michael) Clayton on a smaller scale. I like him because he doesn't play scared."
Prothro can't be scared this year, because right now he's the No. 1 option at the position. As a true freshman, Prothro caught 16 passes for 191 and one touchdown. Now he's expected to be a leader in a group that includes red shirt freshmen Matt Caddell and Will Roach, and older but less experienced players such as Brandon Brooks, Matt Miller, and Marcus McKnight.
"We're going over some of the same plays so I have an edge on some of the other wide receivers because I'm the only one that really played last year," Prothro said. "We threw in a couple of new plays but I adjusted pretty well. I have to be one of the leaders. With me being the only one coming back, I need to set an example for the other ones."
But last season, there were five seniors who saw action before Prothro started to develop later in the season. Heading into the 2004 season, Prothro looks to be the main guy.
Is there any pressure on the true sophomore? Not for this kid.
"Thinking about it, it seems like it would be a lot of pressure, but its doing what you do best, and doing your job," Prothro said.
Whatever it is, Prothro has caught eyes of coaches and defensive backs since he arrived on campus. Prothro was singled out plenty by head coach Mike Shula during most of last fall's practices, and he's a tough commodity for veteran defensive backs to handle.
"He's got a lot of energy as a player," Peprah said. "He's determined and he's a hard worker. He's going to come into his own. Its raw talent, he's going to be a good one."
Prothro also returned kicks last season, and looks to do the same this season. Another Tide mighty mite, Brandon Brooks, returned punts late in the year, but Prothro has been working on that as well. And in an attempt to get the ball in his hands as much as possible, don't be surprised to see Prothro used on reverses this season.
Prothro said he's put on "about five or six pounds" since last season, and dropped his 40-yard dash time from a 4.4 to a 4.35.
But ask him if he feels like a veteran, and he's quick to tell everyone to slow down and realize that for right now at least, he's still just a kid.
"Not yet," Prothro said. "I have a long way to go. I still consider myself as a rookie. I still have a lot to learn about the game, and until I learn it, I'll consider myself still a rookie."