Danny Breeden, older brother of fellow Major Leaguer Hal Breeden, had a long career in AAA with a few big league stops. At one point, he even retired when the Cubs tried to send him to the minors in 1971.
He came back to play a few more years, and a few more deals.
Baseball Reference lists a 1973 purchase by the Padres from the Cubs, and a 1974 trade from the Padres to the Cardinals....but that doesn't explain a mid-1973 switch from the Hawaii Islanders (Padres AAA team) to the Phoenix Giants (SF AAA team).
We find an article from the June 18, 1973 edition of the Arizona Republic...
So we have a trade involving THREE former major-leaguers that was previously unknown.
Another republic article says the trade happened in the first week of June. Score!