Two choices:
(1) Load all three of those guys onto a spring training team, make them all Set Up A (and set all their other settings the same) and ask for Sparky's "recommended setting". Compare that to the "recommended setting" for your AAA guy, and you may be able to narrow it down.
(2) Use your AAA guy for a while until he shows fatigue. Once he does. hold your mouse over his fatigue rating and find out how far over his pitch count he is. From that you should be able to determine which real player he is.
AAA RPs are often tough to pin down. Sometimes you just can't know for sure, but usually in those cases the possible players are so comparable that it doesn't really matter.