"I'm fine with what happened today," Zimmer said. "Better results are always nice, but this time of year it's, 'Who cares?'"
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Zimmer -- ranked by MLBPipeline.com as the Royals' No. 9 prospect -- was more focused on improving his mechanics and arm slot, and just getting that first start out of the way.
"I thought it was all right," he said. "I wasn't really going into it worried about results. I thought I made some good pitches. I made some bad pitches, too. That 0-2 pitch I left up. But that's going to happen this time of year."
That 0-2 pitch was a fastball to Rangers outfielder Ryan Rua in the first inning. Rua roped it over the left-field fence for a two-run homer.
"I wanted it up-up," Zimmer said. "But I left it up-middle. It was 0-2 and I was trying to raise his eye level a little bit. Left it around the belt, and you can't do that to a hitter like that. It happens."
Zimmer's velocity hit 95 mph twice during the first inning and it sat around 93-94. By the second inning, though, that velocity dipped to 90-91.
"I was just a little tired," Zimmer said. "That was the first time I had a second up. The more times you sit down and get back up, it will kickstart and wake up your arm a little more.
"We'll see how I feel tomorrow. I didn't feel great and I didn't feel terrible, which is usually how I feel this time of spring."
Zimmer said his arm slot has dropped a bit since he had thoracic outlet syndrome surgery last August.
"Yeah, a little bit," he said. "I've been working on some different things. I definitely feel like there's more to work on. We've been trying to keep the arm stroke a little shorter. As you throw more, you tend to find your more natural slot. I'll get there."
Jeffrey Flanagan has covered the Royals since 1991, and for MLB.com since 2015. Follow him on Twitter @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.