The Seattle Mariners have one of the strongest farm systems in the major leagues right now. General Manager Jack Zduriencik has done an excellent job filling the ranks from the bottom up since taking over in 2008.
Because of that bottom-up strategy, the Mariners' Triple-A affiliate, the Tacoma Rainiers, is comparatively the weakest link in the chain (i.e. they aren't as much of a standout in their league).
The fact that the Double-A Jackson Generals could probably beat the Rainiers in a game indicates that the first minor leaguer to get called up could very well be from the lower level, which isn't actually uncommon.
Anyway, mid-June is usually when the major league team will make its first significant call-up—that's when current second baseman Dustin Ackley joined the team last year.
The M's have fared relatively well thus far this year, managing a 15-18 record through about a month-and-a-half of regular season play. Every game presents a slightly altered lineup from the previous contest, which is Manager Eric Wedge giving himself a look at a variety of young players in a variety of slots in the field and batting order.
Shout-outs go to Kyle Seager, Alex Liddi, Jesus Montero, John Jaso, Tom Wilhelmsen and Lucas Luetge for great performances so far.
So, who's going to join those guys as the first minor league call-up of the 2012 season? Here are my four candidates in order of increasing likelihood.