|The athletic Johnson's journey from position to position and toward the NFL appears to have him on course to be drafted in the first round as a potential franchise left tackle. He was a high school quarterback who began the 2010 season at Oklahoma as a tight end before switching to defensive end midway through the season. He transitioned to the offensive line for 2011, starting 12 of 13 games at right tackle before starting 11 of 13 on the left side in 2012 and earning all-Big 12 second-team honors. Johnson's athleticism, natural abilities and versatility made for an apparently easy switch last year and have his stock rising as one of the most valuable commodities for NFL teams. "I never thought it was going to happen, but everything is going by so fast now,'' Johnson said. ``Just trying to grasp it all is kind of difficult.'' His biggest assets are his exceptionally quick feet, which allow him to adjust to pass rushers' moves and seal the edge well, and he's explosive at getting into position off the snap. He uses his powerful hands and 35-inch arms to keep defenders at a distance, and his quickness allows him to pull effectively on running plays and get upfield for second-level blocks. Johnson doesn't lack for lower-body strength either, generating push on runs and finishing blocks well, and he plays with the edge, attitude and drive that coaches love in offensive linemen. A stellar performance at the NFL combine confirmed him as a top prospect, as he earned an overall grade of 86.9 out of 100. He ran a 4.72 in the 40-yard dash, second among offensive linemen, and was also among the top performers at his position in five drills. He hit 34.0 inches in the vertical jump (third), 9 feet, 10 inches in the broad jump (first), 7.31 seconds in the 3-cone drill (tied for third) and 4.52 in the 20-yard shuttle (fifth). That followed an outstanding week at the Senior Bowl that had already substantially boosted his stock. Johnson is somewhat raw and inexperienced, needing work on his technique, but that's also indicative of a potentially big upside. He may also need to add some muscle, but the overall package of skills and potential at a premium position should still guarantee him a spot in the top 20 picks, if not the top 15.