Holmberg struck out a career-high 12 batters Monday, but he gave up two unearned runs on four hits and a walk over seven innings in Class A South Bend's 2-1 loss on the road to Bowling Green.
The 19-year-old D-backs farmhand, originally selected by the Chicago White Sox in the second round of the 2009 Draft, lowered his ERA from 6.00 to 4.09, but is still without a win in the Midwest League.
"It is a team game and it's not a big deal that I didn't get the win," said Holmberg (0-3). "I know that if we grind hard every day, the wins will come.
"A lot of things that I have been working on with my pitching coach and in the bullpen and through Spring Training were good tonight. We were setting them up and knocking them down."
The Silver Hawks took a 1-0 lead in the first inning on Chris Jarrett's RBI triple, but Bowling Green tied the game in the bottom of the second.
With one out, Holmberg hit Nick Schwaner with a pitch. Schwaner stole second and Ramon Castillo -- making his first start behind the plate -- threw the ball into center field to allow him to advance to third. A two-out RBI single by Kevin Keirmaier knotted the game at one apiece.
A similar situation happened in the bottom of the fifth when Keirmaier stole second and went to third on Castillo's throwing error. He scored the go-ahead run on a two-out RBI single by Hector Guevara to put the Hot Rods in front for good.
Holmberg tried to use Bowling Green's aggressiveness against them. He picked a pair of runners off, and two others were thrown out trying to swipe second. In general, Holmberg thought they executed their game plan well.
"They seemed to be a very aggressive team," he said. "They took big leads off of first base and they were leaning a lot. It is a bit upsetting that their two runs scored like that, but that is part of the game and you have to let the cards fall where they may."
Other than the two unearned runs, Holmberg thought he pitched well. He retired the side in order three times and said his control was sharp.
"My fastball command was good and my two offspeed pitches -- my curve and my slider -- were okay," Holmberg added.
"I haven't struck this many out since maybe high school. I definitely hadn't done it as a pro, but if gives you a lot of confidence to know that you can throw every pitch where you want it."
Sent to Arizona with Daniel Hudson in the deal that netted Edwin Jackson for the Chicago White Sox, Holmberg's previous high was nine strikeouts -- achieved twice in his final three starts pitching for the short-season Missoula Osprey at the end of last year.
He was a combined 2-5 with a 4.17 ERA between Missoula and Great Falls last season after posting a 2-2 record in 14 appearances -- seven starts -- with Bristol in the Appalachian League in '09.