Here's a pair of under-the-radar Triple-A pitchers who might contribute this year: lefty Justin Marks of the Kansas City Royals and right-hander Taylor Hill of the Washington Nationals.
Justin Marks, LHP: Marks was originally drafted in the third round in 2009, by the Oakland Athletics out of the University of Louisville. He came to Kansas City along with right-hander Vin Mazzaro in the November 2010 David DeJesus trade. Marks has often been overlooked when Royals prospects are discussed: there are always guys who throw harder or put up more dominant stats, but he's remained a consistent inning-eater. He posted a 4.34 ERA between Double-A and Triple-A last year with a 129/66 K/BB in 144 innings. For Omaha this year he has a 2.70 ERA in 10 innings with a 9/5 K/BB.
Marks was promoted to the big leagues last week when the Royals needed a pitcher and got knocked around in his only appearance, giving up four hits, three walks, and three runs in two innings against the Minnesota Twins on the 20th. He's back in Omaha now but should receive further chances. Marks is a four-pitch lefty with an 89-90 MPH fastball plus a curve, slider, and changeup. When I've seen him in the minors, at times he looks like an efficient finesse pitcher with adequate stuff to start, but at other times he gets too nibbly against right-handers and looks like a future LOOGY. Bullpen work seems much more likely at this point.
Taylor Hill, RHP: A sixth-round pick out of Vanderbilt in 2011, Hill has pitched very well so far this year for Triple-A Syracuse, posting a 1.80 ERA in 25 innings with a 24/4 K/BB and a 1.88 GO/AO. He was effective in 2013 as well, with a 2.95 ERA and a 104/29 K/BB in 165 innings combined between Double-A Harrisburg and Syracuse.
Despite his statistical success, Hill doesn't draw glowing scouting reports. The 6-3, 230 pound right-hander uses a four-pitch mix with a fastball, slider, regular changeup and occasional splitter. Reports on his fastball velocity are all over the map, reported anywhere from 87 to 93 MPH. I don't have a current velocity report from Syracuse (chime in with one if you have something from a reliable source or a personal observation), but his strikeout rate has taken a step forward this year, which is always a good sign. He has potential as a back-end starter or bullpen arm and is a good bet to see the big leagues later this year if he keeps pitching like this.