PITTSBURGH -- It was only three weeks ago that Aaron Thompson was trudging through his fourth season at the Double-A level. The results had been better than they were a year ago, but the numbers were hardly worthy of much hype.
Need prompted the Pirates to promote Thompson to Triple-A earlier this month. And need brought the 24-year-old left-hander up another rung to Pittsburgh on Wednesday, where he was needed to spot start.
Thompson didn't get the win in his Major League debut, but the Pirates did, thanks in large part to Thompson's effort. The lefty gave Pittsburgh 4 1/3 scoreless innings to send the Pirates to a 2-0 victory over the Brewers in front of 18,013 at PNC Park.
With the win, the Bucs earned a series split against the Brewers, who had entered the series with a 12-game winning streak against Pittsburgh.
"That was fun to watch, fun to watch," manager Clint Hurdle said. "Big day for Aaron. We're proud of him. He stepped into a difficult situation and he stepped up."
Thompson drew one of the league's most prolific offenses as his first Major League assignment, though he hardly seemed fazed. Looking poised and polished, Thompson retired Ryan Braun and Prince Fielder with a runner at third in the first inning and settled in nicely from there.
A double play helped to erase a baserunner in the second. Two innings later, Thompson induced a groundout to strand two more. At the end of the frame, his pitch count sat at 60.
Thompson's two-seam fastball and changeup were particularly effective because, just as Brad Lincoln did two days before, he focused so intently on pitching inside.
"Some of the big guys, they don't like it in," said Thompson, who had his parents, brothers and grandfathers in the stands for his debut. "That's something that we've preached all year -- to pitch it in. I think it worked today."
Thompson limited Braun and Fielder to one single in four combined at-bats.
"It seemed he had nice command of all three pitches," Braun said. "He obviously did good, because overall we've been swinging the bats well as a team. We put together some good at-bats and didn't score any runs, and he certainly deserves the credit for that."
Thompson's chance at a win slipped away when each of the first two batters reached in the fifth. With the Pirates leading, 2-0, at the time, Hurdle opted not to leave Thompson in a position to lose.
The limitation on Thompson's pitch count weighed heavily in Hurdle's decision to pull the left-hander when he did. Though Thompson joked, "I would have thrown 200 pitches. I didn't care."
Jason Grilli took over and ensured Thompson's pitching line stayed clean by stranding both runners he inherited.
"Getting into tight spots, I thrive like that," said Grilli, who has now made six straight scoreless appearances. "It's enjoyable to me."
The right-hander went on to provide a huge lift for the bullpen with 2 2/3 perfect innings.
"He was really sharp," Brewers infielder Josh Wilson said of Grilli. "His curveball is really good, and he has the fastball to back it up."
Grilli needed only 33 pitches to record those eight outs, and he did not allow a baserunner in the process. He was rewarded with the win, Grilli's first since Aug. 27, 2009.
"I would rather [Thompson] get the game ball and the win today," Grilli said. "He did a phenomenal job today."
Thompson's impressive start isn't likely to earn him another immediately, though the effort could help the left-hander's standing as the Pirates evaluate internal pitching options this offseason.
Thompson's numbers this season -- a 5.16 ERA in 26 Double-A games and a 0.77 ERA in three Triple-A ones -- aren't among the best in the system. But the Pirates have been encouraged by some of the steps forward Thompson has taken, even if they are not reflected on the stat sheet.
This was Thompson's first year pitching in the Pirates' system. He was claimed off waivers from the Nationals last December.
"I'd like to think that my stuff is good enough to get guys out," Thompson said. "I think as long as you throw strikes, you give everybody a chance to make a play."
The Pirates' offense didn't have a huge day against Brewers starter Shaun Marcum. But they didn't need one. Jose Tabata doubled and scored on Andrew McCutchen's sacrifice fly in the first. Josh Harrison doubled and scored on a sacrifice fly by Neil Walker three innings later.
Pittsburgh didn't advance a runner as far as second after the fourth inning.
The bullpen's string of 4 2/3 scoreless innings on Wednesday was finished off by Jose Veras and Joel Hanrahan. Veras cruised through the eighth, though the same couldn't be said for Hanrahan's ninth-inning appearance.
In his first outing since blowing a save against the Reds, Hanrahan put the potential tying runs aboard with no outs. He responded by striking out the side.
The Pirates' win kept the Brewers from extending their streak of series wins to nine. Milwaukee is now 18-5 in August. Wednesday's victory was the seventh of the month for Pittsburgh.
"You'll take a split," Grilli said. "Against a club doing what they're doing, we'll take it. We'll take it."
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.