Sorry -- I should have provided the data behind my claim, and now I will. "A list of major league 20-year-old regulars is a list half-consisting of Hall of Famers" wasn't a guess and or an exaggeration, it's the literal truth.
Actually it's an exaggeration if you count *bad* regulars, but the claim is literally true of 20-year-olds who are average-to-good regulars. There, names like Mel Ott, Johnny Bench, Al Kaline, Mickey Mantle, Ty Cobb, Frank Robinson, Ted Williams, Ken Griffey Jr, Rogers Hornsby, Jimmie Foxx, Mike Trout, Alex Rodriguez, and Roberto Alomar dominate the top twenty seasons at that age (plus too-soon-to-tell guys like Manny Machado, Bryce Harper, and Jason Heyward).
Willie Mays, Arky Vaughn, Joe Torre, Bill Mazeroski, Eddie Mathews, Fred Lindstrom, Ivan Rodriguez, and Travis Jackson are also in the top-44 list, which is the entire set of "average-and-above seasons by a 20-year-old regular". (As are possible future HoF-ers Alan Trammell and Giancarlo Stanton.) The
only players in that entire top-44 list who didn't have good careers were Tony Conigliaro (destroyed by injuries) and Bob Horner.
Even among the mediocre 20-year-old regulars are a smattering of Bobby Doerrs, Hank Aarons, Robin Younts, and Miguel Cabreras, and very few careers that weren't pretty decent. In, again, real life -- and
not in OOTP.
Here's a list:
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