There's a good amount of subjectivity regarding baseball prospects. With the evaluation of talent being in the eye of the beholder, finding consensus is often difficult. Even Jim Callis and Jonathan Mayo of MLBPipeline.com don't always see eye to eye. They discuss their viewpoints regularly in a feature called Pipeline Perspectives. Submit a topic for them to debate.
The Rockies never have had much luck with starting pitchers. Playing home games at Denver's high altitude doesn't help their cause, but in 21 seasons of existence, they've sent just five starters to the All-Star Game -- none of them more than once.
Only one Colorado starter who qualified for an ERA title ever has posted a mark better than 3.00: Ubaldo Jimenez in 2010. Just one has totaled more strikeouts than innings: Jorge De La Rosa in 2009.
While the Rockies rarely have problems scoring runs, pitching drives their success. Before they started storing balls in a humidor in 2002, they recorded a sub-5.00 ERA just once -- in 1995, when they made the playoffs for the first time. Their only other postseason appearances were in 2007 and '09, when they had the second- and third-best team ERAs in franchise history.
Colorado had the worst ERA in the National League in 2013, and not coincidentally finished at the bottom of the NL West. But the Rockies do have some good news on the way.
In right-handers Jon Gray and Eddie Butler, they have the best pair of pitching prospects in baseball. Jonathan Mayo argues that the Pirates' duo of Jameson Taillon and Tyler Glasnow is superior. While that's debatable, this much is not: No tandem is as crucial to its club's future success as Gray and Butler.
In a Pipeline Perspective written in October, I outlined why Gray was the best prospect to come out of the 2013 First-Year Player Draft, even if he wasn't taken until the third overall pick. After signing for a franchise-record $4.8 million, the University of Oklahoma product capped a strong pro debut by recording a 0.75 ERA and 36 strikeouts in 24 innings in the Class A Advanced California League.
Gray's stuff is even more impressive than those statistics. Both his fastball and his slider graded as the best among MLB.com's newly minted Top 100 Prospects.
Gray can maintain his mid-90s fastball deep into games, and he has cracked 100 mph at times. In addition to his overpowering velocity, his heater also features exceptionally heavy life. When hitters manage to make contact with Gray's fastball, they rarely do much with it.
Gray's slider isn't as consistent, but when it's on, it gives him a second legitimate out pitch. He can run his breaking ball into the upper 80s with sharp bite. The 6-foot-4, 255-pounder made significant strides with his changeup and command in 2013, giving further credence to the notion that he can develop into a true No. 1 starter.
Like Gray, Butler blossomed in 2013. The 46th overall choice in the 2012 Draft, he signed for $1 million and led the Rookie-level Pioneer League in ERA (2.13), WHIP (1.06) and opponents' average (.230) in his pro debut. Butler's stuff seemed a little firmer than it had been at Radford University, and his projection rose from middle-of-the-rotation possibility to No. 2 starter.
Butler's ceiling appears even higher after a spectacular first full pro season. He ranked second in the Minor Leagues in ERA (1.80) and opponents' average (.180), dazzled in the Futures Game and finished the season by allowing two runs in six Double-A starts.
While he can't quite match Gray's pure stuff, Butler has a deeper repertoire and better command. As he has gotten stronger, adding 15 pounds since signing, so have his individual pitches.
Butler regularly pitches in the mid-90s with his fastball, which touches 99 mph and gives right-handers fits because it bears down and in on them. His slider can be devastating as well, arriving in the upper 80s with late break. Butler also has a solid curveball and changeup, and at times he can show four different plus pitches.
Gray and Butler could open the 2014 season together with Double-A Tulsa -- and they could finish it together in Colorado. They have what it takes to become the best 1-2 pitching punch in Rockies history, and to lead a staff capable of carrying the club back to the postseason.
Jim Callis is a reporter for MLB.com and writes a blog, Callis' Corner. Follow @jimcallisMLB on Twitter.