Been meaning to ask this for a while. I understand good coaches mean better players faster, but do they effect boom/bust potential?

Coaches influence development speed only.

Nice to know.

I always assumed a great coach would help my players reach their full potential. But, they will just help them become a star or bust quicker. Interesting.

Does anything affect potential? I just went through a training camp and had 25 people drop, and only 8 get a bump.

Each player is assigned a secret random value for how their potential will trend - it's essentially a normal distribution where most players will stay about where they start, but the outliers can be fairly extreme. Then each TC (and each week sim to a much smaller degree) the players' potential is adjusted again with a normal distribution around their trend. So depending on how far the drop/bump is, it may or may not indicate the long-term trend. A player that drops 15 or 20 points probably will be a bust because the second calculation is unlikely to move them that far, but I've had players drop several points and end up booming in future years as well, or at least back to where they started.

I wish performance added to potential .....

Like Vince Lombardi drafting Ryan Leaf lol

This means I have been REALLY over-valuing coaches.

Unless you have a roster full of very young players who still have a lot of developing to do, coaches are meaningless.

The only exception is that the HC determines your offensive and defensive playbooks, but it doesn't matter if he's any good or not if your players are already nearly developed, or you're fine having the young ones ride the pine while they develop "slower".

Yeah, my takeaway is that it's not really worth spending a lot on a position coach unless you're specifically developing those players.

One feature that has been suggested and I would like to add is a hidden "coachability" attribute that would determine how the coaching staff can improve a player's future potential (or, rather, offset its natural trend). I.e, a player with a high coachability attribute would reduce the probability for him to bust and improve his boom potential for attributes based on his coaching staff hierarchy. A player with low coachability would behave as players currently do. (Or should it even be hidden? Might make for an interesting comparison attribute, and wouldn't tell you too much since the boom/bust is still hidden.)