McDonald, who spent parts of the past two seasons with the Dodgers, primarily as a reliever, entered the game having allowed 17 hits in 12 2/3 innings for Albuquerque this season. He lasted just one inning in his previous start, yielding three runs on three hits and two walks against Omaha on April 18.
After retiring the first nine batters he faced, McDonald walked Round Rock center fielder Jason Bourgeois to lead off the fourth. Bourgeois stole second, then was picked off trying to steal third. Brian Bogusevic drew a walk later in the inning, but was forced at second to end the threat.
McDonald retired the Express in order in the fifth and faced just one batter over the minimum. Round Rock finally broke through for its first hit with two outs in the seventh when left fielder Collin DeLome doubled to right off veteran reliever Juan Perez.
An 11th-round pick in the 2002 Draft, the 25-year-old McDonald's closest previous brush with a no-hitter came as a member of the Class A Columbus Catfish on Aug. 27, 2006. He tossed eight one-hit frames against the Charleston RiverDogs, striking out eight, only to see his bullpen allow a ninth-inning run in a 1-0 loss.
McDonald (1-0) avoided a similar fate Thursday night. Though the Express pushed a run across in the eighth and put the tying run on base in the ninth, Luis Ayala closed out the win for his third save of the season.
The Isotopes' middle infielders provided their offense in the victory. Second baseman Nick Green went 2-for-3 with a solo homer while shortstop Ivan DeJesus doubled, singled and scored twice.
Starter Josh Banks (1-3) took the loss for Round Rock, allowing three runs -- two earned -- on six hits over five innings. He didn't strike out or walk a batter.