The veteran right-hander allowed three hits over two scoreless innings, just five days after signing with the Rangers, as Triple-A Round Rock edged Albuquerque, 3-2, at The Dell Diamond.
Oswalt showed rust early, giving up a leadoff single to Trent Oeltjen, walking Aaron Miles and yielding a single to Josh Fields to load the bases in the first. But he showed why he's finished in the top five in Cy Young Award voting five times, fanning Jeff Baisley and getting Luis Cruz to hit into an inning-ending double play.
"It probably wasn't the best, but that was about where I want to be at as far as velocity and stamina," Oswalt told MLB.com. "[Working out of a jam] makes you focus a little bit more instead of going 1-2-3 pretty quick. You don't get quite as much work in as far as throwing quality pitches. When you get guys on, you have to throw quality pitches a lot.
"I didn't mean to get in a jam. The ball back up the middle, I actually could've caught, but I thought the shortstop was playing over a little bit toward the bag, so I let it go. But I was able to get the big strikeout for the first out, and that was my plan -- to get the strikeout and double play. It worked out pretty well."
Oswalt, who needed 34 pitches to get through two innings, signed with Texas on Tuesday after making 23 starts last season for the Phillies. The 34-year-old right-hander endured a challenging season, suffering through a back injury while posting a 1.34 WHIP, the highest of his 11-year career. Oswalt was 9-11 with 93 strikeouts, the lowest total of his career.
Pitching before a sellout crowd of 11,532 at The Dell Diamond, Oswalt peaked at 94 mph and consistently sat in the low 90s. It was about where he thought he'd be.
"I'm one or two clicks off from where I usually throw, around 93 mph, so I'm getting pretty close," he said. "Changeup was pretty good. One stayed in the zone, guy hit a line drive to third base. But the other ones were pretty good."
Oswalt is expected to throw 50 pitches in his next start.
"I'm going to try to accelerate it a little bit," he said of the Rangers' plan for him in the Minors. "They kind of set pitch counts on different nights, but I'm going to see if we can bump it up a little bit."
Michael Kirkman (5-1) took over for Oswalt and recorded the win after allowing two runs on five hits and striking out three over five innings. Aaron Heilman tossed two hitless innings to earn his first save.
Michael Bianucci slugged a two-run homer, his 11th, and Joey Butler scored twice to pace the Express' offense.
Brian Cavazos-Galvez slugged a solo shot for the Isotopes.