During his brief stint at Rockies camp, Jon Gray watched the big leaguers pitch in and out of trouble. He saw them keep their composure after tough at-bats and continue to attack hitters.

The Rockies top prospect kept those lessons in mind Saturday night when he made his Double-A debut in Tulsa's 7-4 loss to visiting Corpus Christi.

Pitching in front of family members, the Oklahoma native hit Astros No. 7 prospect Delino DeShields with a pitch leading off the game.

"I was pretty amped up," Gray admitted. "[My fastball] was a little bit elevated at times; it wasn't where I want it to be."

After the Hooks scored four runs over the first three innings and after Gray (0-1) made an errant pickoff attempt and plunked DeShields again, the third overall pick in last year's Draft remembered what he learned earlier this spring.

"I went to the 80s on some of them and I can't do that. I need to pitch with conviction every time," said the 22-year-old right-hander, whose fastball reached 99 mph at ONEOK Field. "I got kind of mad at myself, but I kept my mound presence intact and I said, 'I'm going to go after these guys.' Then I was pretty dominant."

MLB.com's No. 14 overall prospect settled down and did not allow another runner past second base over his final three frames. Aside from hitting DeShields, Gray said he felt in control, throwing 53 of 88 pitches for strikes and issuing just one walk.

"A lot of it is just working on the mental game, seeing the target rather than just thinking about the mechanics," the Oklahoma University product added.

Gray made a seamless transition after the Draft, overpowering opponents in the Pioneer and California leagues to the tune of a 4-0 record, 1.93 ERA and 51 strikeouts over 37 1/3 innings. Moving up a level to start his first full Minor League season presented him with his first brush with adversity.

"Everything feels good. I'm ready to get back out there, just need to work on the things that I've been working on," Gray said after his first professional loss. "It's the first game of the year and it will all come together. I just have to focus more."

With DeShields and Rene Garcia stealing bases for Corpus Christi, one area for improvement is pitching out of the stretch. Gray already noted that his body was too elevated.

The Drillers almost got Gray off the hook, rallying for two runs in the eighth and loading the bases with two outs in the ninth. But Andrew Robinson came on and struck out Taylor Featherston for his first save of the season.

Garcia and Preston Tucker homered, while Andrew Aplin collected three RBIs for the Hooks. Corpus Christi starter Luis Cruz (1-0) allowed two runs on five hits while striking out five over five innings.

Ryan Casteel smacked a two-run homer for Tulsa.