The starters were not only lower in skillset, but also more tired and less experienced, why it is not working as it says in the manual? Otherwise how can I fire the coach who's making those decisions on 4th quarter? :D
If it makes you feel better, I can certainly confirm that coach doesn't always let your players play maximum minutes even if you order him to do so (instead of asking to win game in 4th quarter)... :P So I know how you feel and I've had urge, and have of course fired many coaches (well, not just because of that, but you'll get my point) and I have bad news for us: they're all the same, can't seem to be able to read or comprehend instructions and firing one doesn't fix the problem xD
To be honest I had higher expectations for someone I pay tens of thousands of dollars per week, but hey, maybe I was just overly optimistic ;P