Gray, 22, a power pitcher from the University of Oklahoma, stayed in the 94-95 mph range while pitching the seventh and eighth innings. He also mixed in his slider and changeup, and basically treated his first time on the mound in a Major League uniform like the first time out for anyone, anywhere.
"I wasn't really nervous, but I may have been a little amped up and quick to the plate," Gray said. "I just treated it like a normal game, like, 'I've got to get this guy out.' I was a little fast to the plate, but I also had some good location, especially with my changeup -- it's come a long way, and I saw some good signs today."
Newly acquired lefty Brett Anderson started the game for the Rockies, who decided to hold Gray until late, which allowed him to collect his thoughts and relax. He had the composure he needed.
The second batter he faced, Jabari Blash, worked a walk on a 3-2 pitch. Gray induced a flyout to right from D.J. Peterson -- last year's top Draft pick for the Mariners -- then allowed a Michael Dowd single to put runners at first and second, and ended the seventh on Leon Landry's grounder to short.
Gray struck out Tyler Smith looking and Ketel Marte swinging to open the eighth. Jeffrey Zimmerman singled before Gray ended his work with a grounder from Jack Reinheimer.
Gray finished with strikes on 24 of his 37 pitches.
"He threw strikes and that was the key," Rockies pitching coach Jim Wright said. "He was worrying about being too quick. We were seven runs down, so I told him to relax and throw strikes. That's what he did."
The Rockies invited Gray and 2012 supplemental-round selection Eddie Butler, another live-armed right-hander, to Major League camp and are seeing how they compete. Many experts believe they both could be in the Majors quickly, and the Rockies appear prepared to let them take as little or as much preparation time as needed -- and as their talent and the team's needs dictate.
"I thought Jonny did a nice job," Rockies manager Walt Weiss said. "He's got easy velocity. He threw some good changeups and some good sliders. For the first time out, I thought he threw the ball really well."
Butler was scheduled to pitch Monday night against the D-backs at Salt River Fields at Talking Stick.
Gray, who compiled a 1.93 ERA between Rookie-level Grand Junction and Class A Modesto in nine starts last summer, knows there is plenty of time to build up to his high-end velocity.
"I'll probably need a few starts just to try it, but I'm probably going to wait until the season to do that," Gray said. "I'll wait for the most part and kind of take it easy."