Mel Kiper Jr. shares the adjustments he notices in Lamar Jackson's play that have earned the Louisville QB a spot on Kiper's 2018 Big Board. (1:51)

In this edition of my Big Board: Two new quarterbacks enter, including the reigning Heisman winner, plus I have a new No. 1 offensive tackle and No. 1 wide receiver from my preseason rankings.

A reminder:

The write-ups here won't change much week to week. Only a few games have been played so far, so I'm still waiting to see who has taken a step forward.

Keep in mind that several prospects listed here have started only one season, so my projections are based on size, athletic ability, statistics and what I hear from people around the league.

Speaking of size, what's listed here is provided by the school. These numbers could vary greatly when players show up at the NFL combine. True height and weight really matter for almost every position.

Note: One asterisk denotes player is a junior, and two asterisks denote player is a redshirt sophomore for the 2017 season.

1. **Sam Darnold, QB, Southern California

Darnold has everything NFL teams want in a starter. He has a big frame (6-foot-4, 225 pounds), makes quick decisions and is an accurate, natural passer. He completed 67.2 percent of his passes last season and ranked second in the nation in Total QBR (86.8). Darnold has thrown too many interceptions to start the 2017 season -- four in two games -- and he has an unorthodox, long delivery that will have to be tweaked. But the third-year sophomore is an exciting prospect who could go No. 1 overall in April's draft.