"This is a good opportunity for him to show everybody really, truly, how good he is, and he is that good," said Kieboom, the Nats' No. 21 prospect. "I'm excited to see what happens here, the rest of May and the rest of the time I'm with him."
So far, so good. Giolito was on his game in Harrisburg's 2-1 walk-off win over Portland, whose lineup featured Red Sox No. 3 prospect Andrew Benintendi. The 21-year-old right-hander set a season-high and tied a career-high by going seven innings -- allowing one run on four hits, walking one and striking out a season-high six. He threw 70 of his 106 pitches for strikes.
"It was definitely my best outing this year," Giolito said.
Filling up the strike zone was a good sign for Giolito, who entered the day with 5.6 walks per nine innings this year, up from 3.2 during his eight-start stint with the Senators late in 2015. Before his promotion to Harrisburg, he had walked 2.6 batters and struck out 11.1 per nine innings at Class A-Advanced Potomac.
"Earlier in the season, I was so erratic," Giolito said. "I would fly open. I would drift forward. My mechanics were a mess. It's gotten better past few outings, but today, as soon as I felt myself do something wrong, I was able to fix it the next pitch."
Even before Wednesday's performance, Harrisburg pitching coach Chris Michalak had begun to see signs of what Giolito showed him late last year. Some of that was physical, such as repeating his delivery and getting better angle on his pitches, taking advantage of his imposing 6-foot-6 frame to throw downhill.
But Michalak has also noticed a more relaxed version of Giolito, one who isn't pressing as much in response to internal and external expectations. After all, this could be the year the former first-round pick pushes his way up to the Majors, but through five outings he carried a 5.30 ERA and a 2.04 WHIP.
"For the most part, I thought he did a really good job of handling it and not showing it outwardly," Michalak said. "I think he got frustrated at times and I think he'd be the first one to admit it. We've had some talks, and I've told him that we're trying to get him to focus a little bit more on what he can control."
Giolito has what Michalak describes as "three above-average Major League pitches," in his mid-90s fastball, hard curve and changeup. But without command, that nasty stuff can't reach its potential, as Double-A hitters are less likely to chase and more likely to punish center-cut mistakes than their Class A counterparts.
For the most part, Giolito had that command when he needed it Wednesday. Following Benintendi's RBI single in the first inning, Giolito retired 19 of the final 22 batters he faced, capping the outing by burying a curve to whiff Portland's Aneury Tavarez and strand a runner at second.
It's the sort of performance Kieboom saw coming.
"To me, the sign of somebody who's great is not somebody who just dominates all the time," Kieboom said before the game. "It's somebody who faces adversity, and next thing you know, they go out there and they're battling back, and it's like, there he is, there he goes, and boom, they take off again."