Some guys show up after not doing a lot in college and hit it out of the park in the various drills. They go from fairly obscure prospects to 1st and 2nd rounders based on their "measurables". They end up drafted higher than their college tape supports, are often thrust into the action faster than their lower-drafted counterparts, and struggle as a result.
Other guys show up after putting a lot of good tape together in college and, for one reason or another, don't do so well in the drills. For whatever reason, those guys were off that day, and they end up falling down draft boards as a result. But unless whatever was wrong at the Combine is something they can't fix or that doesn't resolve itself, this class of player ends up going later with fewer expectations, often more time to acclimate to the pros, and because they are talented players, usually thrive at that level.
Dantzler is one of those latter players IMHO. This is from the Walterfootball (https://www.walterfootball.com/draft2020CB.php) eval of him. Emphasis is mine:
So Rick Spielman gets Gladney in the late first after trading down for more picks, then comes up with Dantzler in the 3rd not because Dantzler's tape supported a 3rd round grade, but because he had a bad day at the Combine and he's a little lean.4/22/20: Multiple team sources say Dantzler has really good tape, and he was trending toward being a late first-round candidate, but his slow combine 40 really hurt him. Dantzler also is very lean, and his skinny frame has evaluators worried about him holding up in the NFL.
In 2019, Dantzler recorded 40 tackles with two interceptions, eight passes broken up, one forced fumble and a fumble recovery. He is a solid corner who is tall, physical, a willing tackler, and has good instincts. If Dantzler were thicker and ran a little faster, he would be a mid first-rounder as he produced a lot of good tape over his collegiate career.
6/22/19: Team sources have said that Dantzler was a player who jumped out at them in 2018 despite them not watching him closely because he was yet to be draft eligible. The sophomore totaled 43 tackles with nine passes broken up and two interceptions for 2018. Dantzler has good size, and the questions will be how well he runs and if he is fluid enough to maintain coverage and prevent separation.
Spielman effectively got 2 1st round CBs in this draft, and he did it with some flair to boot. Dantzler is going to be a good one.