The 2018 NFL Draft is just six days away, and rumors are flying left and right.

Four quarterbacks are expected to go high: USC's Sam Darnold, UCLA's Josh Rosen, Oklahoma's Baker Mayfield and Wyoming's Josh Allen. But there is another QB who is receiving first-round buzz, albeit with less hype.

What makes Louisville's Lamar Jackson such a unique and intriguing prospect is exactly what labels him a frustrating NFL enigma.

Had Jackson been eligible for the 2017 Draft, he might have been the first overall pick, even over Myles Garrett. After all, Jackson had just led Louisville to a 9-4 record, winning the Heisman Trophy after a legendary season in which he threw for 3,543 yards and 30 touchdowns. Pretty good stats, and that's before counting his impact in the run game.

Jackson ran for 1,571 yards on 260 carries, scoring 21 TDs. That's a total of 51 touchdowns in a season, an average of about four per game. Defenses were almost completely helpless when playing the Cardinals; Jackson could score whenever he touched the ball, which was every play, as he was the QB. He was faster than any defender on the field, so he couldn't be contained within the pocket. And when defenses keyed in on the run game, he made them pay with his arm.

Jackson is the closest thing the NFL has seen to Micheal Vick, since, well … Micheal Vick. Yet he probably won't even be a top-10 pick.

Teams just aren't exactly sure what they'll get with him.

Physical traits

Jackson's arm is very strong. He has the ability to drive the ball deep downfield, as well as fire the ball into tight spaces with velocity. This throw shows off both his strong arm and his lightning-fast release. He just flicks his wrist and the ball jumps out of his hand. This quick release combined with his athleticism helps to keep his sack count low.

Jackson didn't run the 40-yard dash at the NFL combine or Louisville's pro day, but he has run a 4.34 in the past, and is clearly faster than most other players in college football.

Jackson stands 6-foot-3 and weighs 200 pounds. He has ideal height for the position, but his thin frame is worrisome. He is not big enough to consistently take hits at the NFL level, especially when running with the football. He needs to add at least 15 pounds and learn to slide more often, in order to reduce the number of unnecessary hits he takes.

Jackson also struggles with consistent accuracy. As his displayed at both the combine and his pro day, his deep accuracy is lacking, as he will completely miss his receiver every so often. He also needs to improve his ball placement to all areas of the field, as he doesn't always lead his receiver or put them in a position to lessen a hit over the middle.

Mental aspect

Playing QB in the NFL is a cerebral task. Players must digest and memorize an entire playbook filled with plays, calls, audibles, formations, schemes, concepts and looks. They have to be able to diagnose what the defense is showing both before the snap and during the play.

Jackson's college offense relied heavily on the run/pass option, but it also included some pro concepts, as head coach Bobby Petrino has coached in the NFL previously.

Jackson did have to make reads and go through progressions, but they were not extremely detailed ones, and he had a tendency to run if his first and second options were not open. He will need time to learn an NFL system before he has any success in the pros.

At the NFL Combine, players take a test known as the Wonderlic. It's a basic standardized test, designed to gauge how well players are able to think and deduce under pressure. It can't be used to measure whether someone is extremely intelligent, but a low score is a concern. Jackson finished with a score of 13, and the next lowest mark was Baker Mayfield with 25.

While it's not a reason to completely dismiss Jackson as a prospect, it is a red flag. Especially for a quarterback, who is the most scrutinized player on a team.

NFL fit

Jackson's best fit in the NFL is a team where he can sit and learn behind an established veteran QB for at least one year. The Arizona Cardinals, Baltimore Ravens, and Los Angeles Chargers pick at 15, 16 and 17, and could all be options. If those teams pass on him, he may fall into the second round. He needs a supportive environment where expectations for his first season are low.

Jackson could become a better Micheal Vick, or he could be out of the league in five years. Which way he goes will depend on the situation he starts in. Jackson will be one of the more interesting players to watch in the green room on Thursday.