All 1939 Managers, Going ahead and sending this report out now that the regular season is over.  
I will list player by team (Mgr), player name, primary position, and what season they return.  
Or if their career in MLB is over, they will just have an (*):

Borger Gassers (Baxter)
Joe Vosmik, OF (1940)
Tuck Stainback, OF (1940)
Jim DeShong, P *

Brunnerville Bean Brewers (Brunner)
Jim Henry, P *

Fairfax Atlantics (Peterson)
Joe Callahan, P (1940)

Detroit Titans (Meyerings)
Roy Hughes, 2B (1940)

Montreal Royal Giants (Barkun)
Bob Joyce, P (1946)

New Haven Whiffenpoofs (Williams/Lauer)
Ossie Bluege, 3B *

San Diego Glaziers (Lehman)
Lynn Myers, SS *
Bud Hafey, OF *
Legrant Scott, OF *
Joe Krakauskas, P (1940)

San Francisco Seals (Ungashick)
Wally Millies, C (1940)
Whitey Wietelmann, 2B (1940)
Bud Bates, OF *
Nino Bongiovanni, OF *

Schaumburg Blue Sox (Rahn)
Tommy Carey, 2B (1940)
Lou Chiozza, 3B *

The following teams had no players lost to 50% in 1939:  
Brooklyn Dodgers (Murphy), Louisville Colonels(Applegate), Frankfort Frogs (Plunkitt), New York Mutuals (DeZarlo), & West Baden Sprudels (Ryan).