Butler, hoping to stick after spending parts of the last two years in the Majors, retired the first 11 batters, but made some key mistakes in a 6-3 loss Tuesday night.
In other words, there will be growing pains for Gray, the third overall choice in the 2013 MLB Draft, and Butler, taken 46th overall in 2012. But they demonstrated signs that they can be effective.
Gray's work Monday represented the most consistency the Rockies have seen from him at the big-league level. In his first start, he struck out 10 against the Dodgers, but lasted just five innings and ended up with a no-decision in a Rockies win. Against the Pirates, he couldn't finish off a disciplined set of hitters and wound up throwing 96 pitches (63 strikes) in just 3 2/3 innings.
But Gray put it together and overpowered the Padres in his hard-luck loss.
"I'd suffer through an outing like Jonny had the other night anytime," Weiss said. "He was outstanding. I see him taking big strides."
Butler made an encouraging relief appearance last week when called up from Triple-A Albuquerque.
In his first start this year, Butler displayed a solid two-seam fastball and arguably his most effective slider, but his next step will be taking more speed off his changeup. The outing turned when Matt Kemp swatted a changeup over the center-field wall in the fourth, and the next batter, Brett Wallace, also homered. The Rockies will look to build on the stretches when Butler controlled Padres bats.
"I was encouraged by Eddie's outing last night, although he ran into some trouble in the middle innings," Weiss said. "I thought the stuff was as good as I've seen from him at the Major League level. I think both guys are in a good place.
"The slider has gotten better for him. It's the changeup that's a little firm, not a lot of separation there. But as long as the command is good and he's staying behind the sinker and he's got some depth to the sinker, he'll be very effective."
Thomas Harding has covered the Rockies since 2000, and for MLB.com since 2002. Follow him on Twitter @harding_at_mlb, listen to podcasts and like his Facebook page. This story was not subject to the approval of Major League Baseball or its clubs.