Josh LeRibeus doesnt remember the precise play, but he knows about when it happened.At some point during Mondays practice, the Redskins rookie realized that he belongs, that he can block NFL linemen and linebackers.Youre like, these guys are so good, theres no way you could ever get there, LeRibeus said Wednesday. But then you get in there, and its, Oh, I can do this. That starts to build your confidence.The Redskins selected LeRibeus in the third round of Aprils in the hopes the SMU could product could serve as a backup guardcenter this season and eventually develop into a starter.The uncertainty surrounding left guard Kory Lichtensteiger, however, has accelerated the schedule for LeRibeus.On Monday, Lichtensteiger had a second surgical procedure performed on his right knee and is expected to miss the remainder of the preseason. Since then, LeRibeus and Maurice Hurt have been seen time with the first team at left guard. (During OTAs and minicamp, LeRibeus received ample time at center, another position the Redskins envision him playing.)The moment Lichtensteiger had surgery, I got switched to guard, LeRibeus said. Its a great chance to realize what all I needed to work on at guard. Right now, its just work on the technique, work on the assignments.The biggest adjustment for LeRibeus has been a common one for first year players: the speed of the pro game. He prepared himself for the leap his junior year at SMU when he shed more than 60 pounds by switching to a healthier diet. The Redskins roster lists the native of Richardson, Texas, at 6 foot 2, 315 pounds.It just feels like a whole different level, he said. The practices out here are more intense than any of the games were in college.LeRibeus said he doesnt have a feel for how the position battle will unfold or even how much hell play this season. But he does know the next few weeks will be critical.Im sure preseason will determine a lot of that, he said.Indeed, it will. If Lichtensteiger is not ready for Week 1, its entirely possible LeRibeus will get the nod.And if that call comes, hell be ready.Its night and day, LeRibeus said of his comfort level. I remember that first time I went out there, I was all over the place. Its gotten a lot better.