One ball left the infield, a fly ball by Dexter Fowler. After falling behind 3-1 to leadoff man Eric Young Jr., Perez took a deep breath, controlled his adrenaline and then took control of his assignment.
"For me, 95 percent is right here in the mind," Perez said, pointing to his head. "The other five is physical. Attack the zone. This is a big opportunity for me. They're going to see how I throw on the mound, my body language on the mound."
Perez said he studied former Rangers pitcher C.J. Wilson and the determined look on his face when the lefty used to take his sign and go right to work.
"That's what I do -- go to work, fast," Perez said. "Working fast is good for me and the defense, too."
Rangers manager Ron Washington liked what he saw of Perez, who was 1-4 with a 5.45 ERA in 12 appearances, including six starts, for Texas in 2012.
"He's been looking like that since he arrived in camp," Washington said. "The experience he got last year, he's picked it up and ran with it. He looks like a mature kid -- all business."
The second starting candidate's Cactus League debut wasn't as impressive. For Justin Grimm, the 24-year-old right-hander from Bristol, Tenn., and the University of Georgia, it was grim for one inning but not bad at all the second time around.
In the third inning, Grimm yielded three earned runs on four hits, including a two-out, two-run single by Tulowitzki.
Three of the first four men Grimm faced produced ringing hits -- a double by Charlie Blackmon, single by DJ LeMahieu and single by Young.
Grimm was in the strike zone, but the Rockies were squaring balls up -- because that's where they were arriving.
"I'm not going to make a very good living up in the zone," Grimm said. "Today's lesson is stay down in the zone. Anybody in this league is going to get hit if they're up."
Bringing his stuff down where it belonged, he had a clean fourth inning.
"Maybe more intensity," he said, asked to identify his early struggles. "Maybe too loose. There's a sense of urgency. Obviously, it's where you want to be [in the rotation]. Just go to work every day so you can establish yourself."
A fifth-round Draft pick in 2010, Grimm was 1-1 with a 9.00 ERA in 14 innings for Texas. The Tigers bruised his ERA with six runs in one inning of work.
"He's going to do what he's got to do, and I'm going to focus on what I've got to do," Grimm said."He put two donuts up. We're two different pitchers."
If their afternoons were a study in contrasts, it is consistent with their styles and approaches. Perez works fast and brings the heat. Grimm is more about finesse, location, precision.
Both have ample time to show what they have before April and meaningful games arrive.
Veteran Colby Lewis, recovering from surgery last July to repair a torn flexor tendon in his right, is hoping to be ready to resume his starting role sometime in May. The target date set is June.
By then, Perez and Grimm -- along with five other peripheral candidates for the rotation spot -- hope to have made an imprint that alleviates any management concerns over the rotation.
Lewis threw 20 pitches off a "half mound," from the lower slope, on Monday and club reports were positive.
Rookies Nick Tepesch and Cody Buckel and veterans Randy Wells, Kyle McClellan and Robbie Ross all will be given looks and could thrust their way into the starting picture.
One thing Perez and Grimm share is a refusal to focus on anything but the immediate personal challenge. They insisted they will not be influenced in any way by the work of the other leading candidate.
"Never," Perez said. "I just think how I can do this, do good and have a chance to stay on the team. I don't think about the other guy. Just focus on what I can do."
Perez did admit he was motivated last season when the call went first to Grimm, on June 16, when the Rangers needed an arm.
"They called that guy, because he threw better than me," Perez said. "I'm not a selfish guy. After that, I said, `OK, I need to do go. I want to be there and help the team.' My mind stayed good."
Perez's call to Texas came 11 days after Grimm's arrival. Perez's ERA in 38 innings (25 strikeouts, 15 walks) was inflated by one bad outing against the Tigers. They roughed him up for four runs while he was getting two outs.
"He's got a great fastball and good offspeed stuff," catcher Geovany Soto said. "He feels like he belongs now. That's the key for a guy coming up. Now he knows what it takes. If he keeps working hard, with that ability, he's going to be just fine."