Btownfan...as someone who still considers that 1964 club my favorite Phillie team of all time, I was quite familiar with that group and can confirm that Gene Mauch called Richie Allen "the greatest player he ever managed" and this was a guy who managed Reggie Jackson, Freddy Lynn, Don Baylor...and Johnny Callison.
As for Callison, he always complimented Allen and said he always told people that it was Allen and not he who was the true MVP of that 1964 Phillies team.
One can only speculate [dream?] of just what Richie Allen might have become with the Phillies IF the Frank Thomas incident had never occurred on July 4, 1965. Why do I say that?
Because the Richie Allen of 1965 [until July 4] was having an even BETTER offensive season than he had in 1964, and his '64 season was one for the ages. I believe he was hitting about .340 and his power numbers were even better than in 1964 until the Thomas incident. From there to the end of the season his average, and play, regressed as the fans blamed Allen for the release of Frank Thomas.
By 1966 Allen's demeanor had changed. Although he had a great season offensively his joy for the game was gone. Mauch commented later that he noticed it also and indicated that what he remembered most about the 1964 Allen was the unadulterated pure joy he displayed on the field.
The most memorable moment I have ever witnessed at at baseball game was a triple he hit against Gaylord Perry at Candlestick Park on July 4, 1964. Watching him racing around the bases, with a key extra inning hit to win the game, still seems to me one of those moments that is transfixed in slow motion in my mind.