when people talk about a players I feel like a lot of times it's really just the person who knows the project best or maybe they wrote a lot of the original code so they have the best idea of how it works. My point being who's an A player in my opinion is not reflective of actual skill per se but rather other factors.
Knowledge of the domain helps a lot! But software engineering and dev tools are also domains that are transferable. I have outperformed coworkers with much more code domain familiarity because I had more engineering/debugging/tooling domain performance, or better ability to design and communicate etc etc.
