The Rangers prospect smacked three solo homers for the Double-A RoughRiders, who came up short in a 13-7 loss to the visiting Hooks.
McGuiness became the 12th Minor Leaguer this season to record a three-homer game and the first to do so in the Texas League. The last RoughRider to accomplish the feat was Tommy Mendonca, who also did it against Corpus Christi last July 22, 2011.
"I was just trying to be selective but aggressive at the same time," McGuiness said. "I was looking for something out over the plate early and trying not to get myself out early."
McGuiness went deep in the second inning, when the game was still relatively close. Corpus Christi had a 4-0 lead, but Frisco scored twice to halve the deficit.
"[Bobby Doran] was just pounding me with fastballs," McGuiness said. "He missed early with a fastball. [On a] 2-1 count, he threw a fastball away behind me. I had a feeling he might come back with it and shortened up my swing. He threw it up and out over the plate, I was short to the ball and it got out to left."
The 24-year-old first baseman did not go deep again until the sixth, when the Hooks led, 11-2. He capped his night with another longball in the ninth.
The fact that Frisco trailed for most of the game might have helped McGuiness achieve his feat.
"The second home run, I worked a full count," he said. "We were losing, 11-2, at that point, so I didn't think [Doran] would throw a breaking ball. I was looking for a fastball middle-in and he happened to throw it right there. And I was able to hit it out to right.
"The third one, they brought in a two-seamer, changeup-type pitcher [Henry Villar]. He got me out the last time with the changeup. I wanted to avoid that and look for a fastball out early. The first pitch was a two-seamer over the plate and I was able to hit it out to left-center."
Even with the RoughRiders behind early, McGuiness said he was confident the team -- with top Rangers prospects like Jurickson Profar (No. 1), Mike Olt (No. 3) and Leury Garcia (No. 8) -- still had a chance.
"We have a really talented team," McGuiness said. "We're never really out of the ballgame, especially in Frisco. It's a pretty hitter-friendly ballpark. Being down, 11-2, we knew we had a chance to spark something at the end and get a late rally going. We fell short, but that's one thing about our team -- we didn't give up until the last out."
McGuiness is batting .252 with 13 homers and 35 RBIs in 60 games with the Texas League All-Star break approaching.
"My first half was not as good as I'd like," he said. "I thought I hit a lot of balls hard that I didn't get much to show for, but that's baseball and you can't worry about results as much. Batting average is kind of an overrated stat but still one of the most looked-at, so I would like to get that up.
"The balls that I do hit hard, hopefully they'll find a gap. And every time you get jammed or break a bat, you'll always take those gimme hits, too."