I don't know exactly what the definition of an A / B / C player is, so take this with a grain of salt. I think managers can give mentorship and advice but it's

I don't know exactly what the definition of an A / B / C player is, so take this with a grain of salt. I think managers can give mentorship and advice but it's up to a person to improve themselves. That mostly comes down to attitude, interest and perseverance. Some people just stop themselves from being better, and give themselves arbitrary limits on what topics they won't learn or areas that aren't in the scope of their job.