Most of the 63 Australians to play in the minors are at the lower levels - only five played AAA ball:
Grant Balfour was good enough at Edmonton to get a brief call-up with the Twins.
Jeff Williams posted an era under 4.00 before getting a chance with the Dodgers.
John Stephens pitched 9 games for Rochester, and struck out more than a batter per inning.
Trent Durrington played 39 games at Salt Lake, slugging an impressive .557.
Travis Wilson (born in New Zealand, but I believe he has Australian citizenship) struggled in a year at Richmond, hitting .243.