3. Letting Pep Hamilton walk
This might not seem like a massive mistake because Justin Herbert went out and had the greatest season in franchise history for a quarterback and proved that he has truly arrived. Herbert was going to succeed regardless of who his quarterbacks coach is, but it would have been nice for the long-term outlook of things to keep Hamilton in LA.
First of all, it would have given Herbert some familiarity in the quarterback room. While Shane Day does seem like a great fit with Herbert, we all know how good Pep Hamilton is as a quarterbacks coach. Just look what he did this season in Houston with Davis Mills. Mills was absolutely horrible when he debuted and over the last month of the season he played better than at least a dozen NFL starters.
Having one more year of coaching turnover would have been good for Herbert and who knows, Hamilton could have become a long-term staple of the coaching staff. While nothing is guaranteed, there is some chatter about Joe Lombardi getting head coaching looks this offseason. If Hamilton was still around, the team could comfortably promote him to offensive coordinator to replace Lombardi and keep the current offensive vision.
This regret is not so much an indication of what the team currently has because the offensive coaching staff in LA is a good one. However, I am a firm believer that if you have a good coach you don't let them go if you don't have to.
It is not like Hamilton left the Chargers for a job promotion. That is something that is out of their control. The team simply wanted to go in another direction and he took the same job elsewhere.
I get the thinking around it and it is by no means a massive regret, but it is something that the Chargers might take back if they could.