Drafted in 2009, he signed too late to pitch. He underwent should surgery in 2010 and missed the entire season, finally getting a clean bill of health three months into the 2011 campaign.
So why is Karns bothering to look back on all that now?
"It was a blessing in disguise," the Nationals prospect said. "When I was rehabbing, I was exposed to a lot of our big leaguers in 2009, 2010 -- anyone from Chien-Ming Wang to Jordan Zimmermann, Stephen Strasburg. I learned and picked their brains, gained the mental aspect of the game. I did the homework before taking the test of actually playing in the games."
And he aced his latest assignment.
Karns pitched a seven-inning one-hitter in the opener of a doubleheader Saturday, striking out a career-high 10, as the Class A Hagerstown Suns beat the Lakewood BlueClaws, 7-1.
The strikeout total "just means I am locating my fastball and my secondary pitches were working as well," said Karns, who faced two over the minimum 21. "It was relaxing to have all that working at the beginning of the game."
Karns (2-0) fanned seven of the first nine BlueClaws he faced before walking Gauntlett Eldemire to start the fourth. Eldemire stole second and scored on Kelly Dugan's one-out double.
"I fell behind [Dugan] and he made a good swing and put the ball in the gap," Karns said. "I have to give him the credit. It was a fastball away.
"After the double, my pitching coach came out and gave me a couple of pieces of advice. He told to me focus on the first-pitch strike. It had taken me 14 pitches to get the first out of that inning."
No one else reached against Karns, who retired his final 11 batters.
The outing -- the 23rd of his delayed career -- was by far the best. The 2009 12th-round pick eclipsed his previous single-game bests in innings (six) and strikeouts (eight), both of which were achieved earlier this month.
Karns made his first start of the season May 10 and fanned eight over four frames in Lexington. A week later at Hickory, he went six and earned his first victory.
The former Texas Tech standout made 13 starts between the Gulf Coast and New York-Penn Leagues in 2011 before beginning 2012 in the Suns' bullpen. He's made four straight starts but doesn't know which role he'll assume going forward. Given how long he's waited to pitch, that seems of little consequence.
"I have felt comfortable this whole year, whether it's out of the 'pen or starting," said Karns, who sports an impressive ERA (2.35) and strikeout total (57 in 38 1/3 frames). "I'm in a comfortable state with my mechanics and everything. The more I go out there, the more success I can have."
The Suns scored four runs in the third against starter Lino Martinez as Cutter Dykstra lifted a sacrifice fly, Jason Martinson singled in one and Steven Souza doubled home two.
Martinez (3-3) allowed four hits and walked three, leaving after three innings.
Nationals No. 20 prospect Matthew Skole produced another run in the fifth by smacked his 10th homer.
The Suns dropped the nightcap, 7-5.