Buch and two relievers allowed just one baserunner and faced the minimum 27 batters as the Kannapolis Intimidators blanked the Asheville Tourists for the second game in a row, 2-0.
On Saturday night, Rienzo struck out 10 and gave up two hits over six innings in Kannapolis' 14-0 romp.
"I thought about that," Buch admitted. "I was going to try to beat Rienzo's two hits. Luckily, I succeeded."
Initially, it didn't look like he would, not after Eliezer Mesa led off the game with a bunt single up the third-base line.
"He got away with it," Buch said.
Catcher Miguel Gonzalez promptly nailed Mesa trying to steal second and Buch retired Avery Barnes and Delta Cleary Jr. to end the inning. He was staked to a lead in the bottom half when Daniel Wagner singled, stole second and third and trotted home on Nick Ciolli's base hit.
The 22-year-old right-hander started to settle in, although he had to make an early adjustment.
"I was using my two-seam fastball and changeup, getting ahead of a lot of hitters," he said. "It started to get to a point in the third inning where they were putting some hard ones into play. So I had to start throwing some off-speed stuff on the first pitch."
Locked in a duel with 2009 Pioneer League Pitcher of the Year Chris Balcom-Miller (1-6), Buch did not flinch. He struck out Barnes and Cleary to end the fourth, recorded two quick groundouts in the fifth and three more in the sixth. Pitching into the seventh for the first time in his brief career, the Pennsylvania native struck out the side.
Told he'd faced the minimum 21 batters, Buch said, "I wasn't thinking of that. It was a one-run game going to the seventh inning and I was just trying to keep the shutout going so we wouldn't lose."
Kannapolis got a little insurance in the bottom of the seventh as Miguel Gonzalez reached on a one-out error by shortstop Carlos Martinez, took third on Juan Silverio's double and scored on Wagner's squeeze play.
Lifted after seven innings, Buch stayed in the dugout and watched Jimmy Ballinger breeze through the eighth and Orlando Santos strike out two in a perfect ninth.
"I wanted to support them. They did a great job," said Buch, who skips rope after each outing to build endurance and work up a sweat.
Building endurance has been key for the 2009 eighth-round pick, who began the season in the Intimidators' bullpen. The White Sox sent him to extended spring training to become a starter, a role he filled at Monmouth University.
"Basically, they liked my pitches, so they sent me back to extended to get up to five innings," he said.
The transition continued last month at Rookie-level Bristol, where he went 2-1 with a 2.45 ERA in four starts. Since returning to Kannapolis earlier this month, Buch is 2-0 with a 0.53 ERA in three starts.
"This was my longest outing," he said. "I was around 12-13 pitches [an inning], maybe 15 sometimes. I got stronger as the game got going, but they're taking it easy with me because I haven't started in a couple of years."