Here's some information as well. Wikipedia didn't have anything specific enough.

www.baseballlibrary.com/baseballlibrary/ballplayers/C/Cleveland_Indians.stm

Looks like 1948 is when Satchel Paige was signed on - and the year they won the pennant. I can see now where the writers were pre-empting Mr. Davis' character - giving his baseball backstories and the integration of the leagues!

Jeff was #4 (at least that's what I'm seeing in episode 27. It could have changed later on, I'm not sure).

This site has the roster for 1946. Looks like #4 was Jack Conway of Tyler, TX:

www.baseball-almanac.com/teamstats/roster.php?y=1946&t=CLE


Mr. Conway died on 6/11/93, so he would have been alive when the show aired. He looks to be more of a baseman -- as I believe Jeff was a hitter and a rightfielder. I'm very rusty on baseball though, it's been years since I dated a guy really into it and have lost some of my osmosis knowledge. :eh