Roberts, 27, made his Major League debut for the Rox in 2015, appearing in nine games and totaling 9 1/3 innings with a 5.79 ERA and a five-to-two K/BB ratio. A longtime farmhand of the Rockies, Roberts was selected in the 25th round of the 2010 draft and posted strong minor league numbers until reaching Triple-A for the first time this season. However, while Roberts has an unsightly 5.12 ERA in Triple-A this year, he’s posted an outstanding 28-to-4 K/BB ratio in 31 2/3 innings there. He’s surrendered a surprising and uncharacteristic 14.2 hits per nine innings in a very hitter-friendly Albuquerque environment due to a freakishly high .443 BABIP. While poor luck and a hitter-friendly environment probably aren’t solely to blame for his Triple-A struggles, there seems to be good reason to expect that Roberts would not continue to allow hits at such an alarming rate.
Gurka, also 27, is a former 15th-round pick of the Orioles (2008). He’s worked to a more palatable 2.86 ERA with 7.6 K/9 against 2.6 BB/9 in 63 innings between Double-A and Triple-A this year. Opposing lefties have hit .208/.310/.264 in 2015 versus Gurka, who will also be making his big league debut when he first takes the mound for the Rockies.