It doesn't happen often, but occasionally, a major-league player will be discussed as a future major-league manager. It happened with Frank Robinson (who's now managing in his 15th season) and Tommy McCraw (who never did manage in the majors, but has been coaching in the majors for most of the last three decades).
Did anybody think Willie Randolph would someday become a manager? To check, I scanned a dozen books by Randolph's teammates and managers. As you might expect, he's not a major character in any of these books, which focus mostly on their subjects and the typical cast of characters (Billy, Reggie, Goose, The Big Stein, etc.). But when Randolph's personality does make its brief appearance, we do learn something:
Thurman Munson (1978): We call Willie "Mr. Personality," because he's always so sullen and silent, but he sure can play second base.