The D-backs' No. 7 prospect allowed just one hit without a walk over seven shutout innings Sunday, leading the way as the Class A Advanced Visalia Rawhide shut out the Bakersfield Blaze, 8-0.
Holmberg (6-3) tied a season high with nine strikeouts, giving him 60 in 55 1/3 frames. Though Visalia made three errors in the game, he faced one batter over the minimum thanks to a double play and two men caught stealing.
"My fastball command today was working pretty well," said Holmberg, a second-round pick by the White Sox in 2009. "It was working well with our catcher [Tyson Van Winkle] behind the plate. We were going with offspeed and breaking balls to make them get themselves out."
After retiring seven of the first eight batters he faced, Holmberg gave up a two-out double to Jaren Matthews in the third. He got out of the frame by inducing a flyout off the bat of Billy Hamilton.
"I started [Matthews] with two sliders and got him 1-1," Holmberg said. "I wanted to speed up his eyes and tried to go in on him. I got it in but it was a little up, he got his hands on it and drove it to the fence."
Over his final four innings, Holmberg set down 10 of the 12 batters he faced -- with both baserunners reaching on errors. The 20-year-old left-hander lowered his ERA from 3.72 to 3.25 in the process.
On the offensive side, No. 11 prospect Bobby Borchering homered twice and drove in four runs for the Rawhide. Repeating at Class A Advanced after spending all of last year with Visalia, the 21-year-old outfielder is hitting .248 with five longballs and 27 RBIs.
"It was great. It's always great when your team scores some runs," Holmberg said. "It's a little overshadowed by [the] High Desert [game] -- about a week ago, we scored 26. The guys were definitely swinging the bats well today."
Holmberg, who was traded to Arizona with Dan Hudson in exchange for Edwin Jackson in 2010, also finds himself back with the Rawhide after making 13 starts for them last season. He put together a 4.67 ERA in those outings, striking out 76 in 71 1/3 innings.
The Florida native said his improved results this season are partially a product of his experience last year.
"It gave me a little confidence coming into this year, knowing what to expect in terms of atmosphere, hitters, things of that nature," Holmberg said. "I just carried that through from last year to this year."