Karns led Class A Advanced Potomac in a one-hitter, stifling Lynchburg for just a single and two walks with six strikeouts over six innings as the P-Nats trounced the Hillcats, 14-0.
The right-hander was picked in the 12th round of the 2009 Draft by Washington, but then had to sit out what would have been his first pro season. His start Monday was the fifth out of his last six outings in which he has gone with at least six innings with one earned run since a callup from Class A Hagerstown in early June.
"I'm really happy for this team," said Karns. "We just came off a rough road trip and to come out and start a new series the way we did, it's very exciting to see how the rest of it goes."
Following the injury, the 24-year-old had to rework most of the mechanics that had carried him through his collegiate years at Texas Tech University. Since resuming his pro career, that effort has proven to be a worthwhile one.
"Coming in here, they emphasized on working with me on cleaning up everything -- starting over and being really dedicated, mechanics-wise," he said. "It's great to be out there playing the way I am after having a couple years out. I couldn't ask more of a comeback."
In his initial return last season, he tossed 18 2/3 scoreless innings with the Rookie-level Gulf Coast League Nationals before moving on to Class A Short-Season Auburn, where he went 3-2 with a 3.44 ERA in eight starts.
This year, he began with Hagerstown and posted a 2.03 ERA in 44 1/3 innings, striking out 61 and walking 21. In 46 2/3 innings across eight starts with Potomac, he's gone 5-2 with a 2.12 ERA, fanning 59 and walking 17.
His ascent through the Washington system the past couple seasons has been a steep one. He said it's gone as smoothly as it has because of what he learned while missing all that time in 2010.
"I had a lot of time to experience the mental aspect of the game and sit back and watch the big leaguers rehabbing -- how they prepared themselves, their approach -- so I got to learn first and then take that out with my play when I was healthy."
On Monday, No. 3 Nationals prospect Michael Taylor hit a grand slam in the first inning -- his first homer of the year -- to set a season high in RBIs. He also doubled and scored three times.
It was his third game this year with multiple extra-base hits and his first since May 25.
"It felt good to get the monkey off my back," Taylor said of the home run. "I didn't know if it was going out or not. I was just trying to get the barrel to it, but I'm pretty sure it's my first grand slam in pro ball."
The 21-year-old is 3-for-6 in his last two games following a 4-for-35 slump that began July 2. For the season he's hitting .226 with a .316 on-base percentage and .336 slugging percentage in 88 games.
"I've just been trying to cut down my swing a little bit, stay short, up the middle," Taylor said. "I think it's definitely making a big difference, I'm picking up the ball a little better."
Reliever Joe Testa followed Karns, throwing one perfect inning before handing off to Adam Carr, who walked one and struck out two over two frames to seal the one-hitter.