Okay, so I understand the Rule 5 draft reasonably well. I understand that Hector Rondon is quite probably going to be a fixture until he conveniently contracts an elbow injury / a nasty cold / the ebola virus on the ninety-first day of the season. But something is worrying me...

My question is this: while researching the success rate of Rule 5 picks (which is what I've been doing in my idle moments) I've found a number of cases of players who were picked and stayed with the drafting club, weren't traded for or waived to remove their Rule 5 status, yet spent significant portions of their Rule 5 years in the minor league system of the drafting team (case in point: Jason Grabowski, drafted by the A's from Seattle in 2001; appeared in 4 games for Oakland in 2002 and 74 games for their AAA affiliate). I know that couldn't happen under the current rules, so I assume that the rules used to be different to what they are now. I seem to recall a recent thread in which someone (Tim H, perhaps) referred to a change of the rules in 2006-ish. Could anyone confirm whether the rules did change, when they changed and what the rules were prior to the change? Thanks