Care to explain your awful defender take?
Edwards' size is a pretty big weakness, as typically guys in the NBA at this size need to be elite at something, and are usually complete liabilities defensively. Edwards is likely not an exception on the defensive end, as he hasn't shown any elite instincts to suggest he can be passable at his size, and his lateral agility is not a strength either. It is possible that he just doesn't really try too much on that end because of his responsibilities on offense, but I'd say it's a long shot that he ever becomes an average defender.
The answer here is different for different schemes and for different times of the season. You can hide a bad defender in the regular season if you scheme for it. In the playoffs, that matchup is going to get heavily hunted and leave you at a disadvantage. In general though, I think what happens is that point guards have both the lowest agency on the defensive end because schemes don't ask much of them, as well as the widest range of abilities, which makes it to where their overall impact runs about similar to other positions.
According to the metrics he was also worth -.2 points on the defensive end to the average player.
Three things
-Carsen is not slower than most guards in the NBA
-Carsen is not an an awful defender, although his height will be an issue
-Carsen's ability to score is what sets him apart. He's an elite scorer at the college level, and some of that will translate into the NBA.
His concerns as a scorer are mostly because of his size as well, since it limits his finishing ability against bigger and longer guys. For a guy with his athleticism, he doesn't really draw many fouls, and his finishing numbers aren't amazing. His Free Throw Rate is only .266, and he shot just 49.2% at the rim. Which puts him in the bottom of the pack comparing with NBA numbers, inevitably that 49% rate will fall in the NBA.
Looking at Purdue's numbers, Edwards was the worst on the team in finishing at the rim this season (save Sasha who took 8 shots there). That's a bad percentage, especially given 17% of those are assisted, but he likely won't be as successful as a finisher at the next level with his lack of elite touch and extension. At times he gets a bit sped up attacking the rim and gets a little out of control. Furthermore, the worst team in NCAA at finishing at the rim was UC Santa Barbara - who was above 50% on the season.
Also had the worst EFG% (behind Eric Hunter) and worst True shot percentage (behind Nojel and Hunter) on the team. Percentages are indicative of success at the next level and generally they do go down with bigger defenders, and more physical defenders.
If you look at the NBA combine numbers from last year, you could make the case that Grayson Allen is much more quicker/athletic than he is. Carsen was middle of the pack in vertical leap, shuttle run, and lane agility, the latter being a good indicator of lateral quickness. In that test he was the 13th worst time, including the 3rd worst among guards. In the 3/4 court sprint (which is a good indicator of speed), he finished dead in the middle behind a few PF/C's and tied with PJ Washington who isn't fast.
Edit: Browsing through the charts, Cassius Winston finished at a 55% rate at the rim, playing against better (overall) competition according to SOS. This is with him being the same height as Carsen (allegedly).