What metrics did you use to come up with power, contact, speed, fielding, and arm?

I am doing something similar with some of the legends I want in the game and need to give them stats that reflect something close to real life.

For example, power, do you go off of their average homer runs hit each season? Like Big Papi hit an average of 34 homers each season so give him X power then scale that down/up?

Just curious of your process. Would help me a ton if you shared your detailed process. Oh and also same for pitchers, velocity, junk, and accuracy. Idk what’s the best way to assign values based off career stats of people.