Eddie Butler, Jayson Aquino among four Rockies pitchers headed to Arizona Fall League

The Colorado Rockies announced on Monday the addition of four players to the Arizona Fall League roster of the Salt River Rafters, for whom the Rockies are one of five feeder teams. The list is headlined by Eddie Butler (PuRP No. 3), who recently earned his first big league win after an up-and-down season spent mostly at Double-A.

Butler tossed six innings of one-run ball on Saturday against the Diamondbacks, allowing only five hits and a walk in a 5-1 victory. The 23-year-old right-hander, who began the season as the No. 17 overall prospect in baseball according to ESPN's Keith Law, posted a 3.99 ERA in 20 minor league starts. He certainly took a step backward this season, but in addition (and possibly related) to having his repertoire tinkered with as part of his development, Butler is just now regaining his arm slot, he recently told MLB's Thomas Harding. Getting more innings should help Butler, who missed more than a month with a shoulder injury after his first MLB start in early June, work through those two issues to build strength and consistency heading into a pivotal season for the 2012 first-round pick.

Jayson Aquino (PuRP No. 21) is another interesting prospect the Rockies will test against the usually stiff competition of the AFL. People who judge pitchers on wins, losses and ERA will quickly dismiss the 21-year-old southpaw; Aquino is 5-20 with a 4.78 ERA in 184 innings spanning 32 starts over the last two seasons. However, he's talked about as a prospect for two reasons: Aquino possesses swing-and-miss stuff and is good at limiting walks. Getting him out of crazy hitters' environments -- and starting at New Britain next year should accomplish that -- will help the club better evaluate Aquino, who breezed through the rookie levels of the organization before struggling at Asheville and Modesto.

Right-handed starter Christian Bergman (honorable mention PuRP) and reliever Kenny Roberts will also suit up for the Rafters this fall, joining Butler and Aquino as well as the previously announced group consisting of Trevor Story, Taylor Featherston, Ryan Casteel and Chris O'Dowd.

Bergman has often looked the part of a viable back-end starter in a major league rotation this season, and that's more of a compliment than you might think. The 26-year-old Californian owns a 5.29 ERA but has walked fewer than two batters per nine innings and has pitched pretty well -- 3.12 ERA in a limited sample -- away from Coors Field. There are several red flags, though: Bergman allows two fly balls for every grounder, surrenders line drives at a 33 percent clip and doesn't strike many batters out.

Roberts, 26, is a finesse left-handed reliever who has walked only two batters per nine innings throughout his five-year minor league career and is coming off a strong season in Double-A. The Tennessee native posted a 2.30 ERA in 47 innings and allowed fewer than a baserunner per inning. He has a 2.33 ERA and 1.048 WHIP while striking out 6.8 batters per nine in 293 professional innings since being drafted 25th round in 2010.

You can follow all of our Arizona Fall League coverage -- and there will be plenty -- here.