Tony Dejak/AP

With the score tied at six in the seventh inning of Saturday’s game against the Indians, Nationals Manager Davey Johnson called to the bullpen and asked for Ian Krol. Twelve days prior, 22-year-old Krol was in Class AA Harrisburg, the major leagues far from his mind. He was the “player to be named later” in January’s Michael Morse trade but the transaction wasn’t completed until late March when Krol was finally shipped to Washington.

In his five outings for the Nationals, Krol has dazzled. He mowed through the top of the Indians order in the seventh with nine pitches — left-handers Michael Bourn and Jason Kipnis — neutralized by his hard, well-placed fastballs. Johnson sent him back to the mound in the eighth and he again made another left-handed hitter look uncomfortable, getting Michael Brantley, to pop out by pounding him inside. In all, Krol threw 20 pitches to get five outs. The Indians made contact on only five pitches and whiffed at four.

In five appearances, Krol has allowed no runs, only one hit and struck out eight batters. He and Fernando Abad have formed a potent left-handed duo in the revamped Nationals bullpen. “[Krol] threw the ball great and goes right after them,” Johnson said. “He’s been a real plus for us, too.”

Krol has done it by throwing primarily his fastball. His fastball sits between 93 and 95 miles per hour. Left-handers that throw that hard are hard to come by, and Krol has made left-handed hitters look uncomfortable with his velocity and command. On Saturday, he tossed 20 pitches and only two of them were curveballs. In all, he has thrown 70 major league pitches and 59 of them have been heaters.

“I don’t like to mess around with offspeed stuff when I get in the game,” he said. “I just go right at the batters. I want to get ahead in the accounts and I want to go at them. [I don’t want to] throw some soft stuff up there and see how far they can hit it.”

At Harrisburg, Krol was doing the same, pounding fastballs, especially inside on right-handed batters. He attributes his success at Harrisburg, and in the major leagues so far, to the simple fact that he is now a full-time reliever.

Krol, drafted in the seventh round of the 2009 draft out of high school, was named the Athletics 2010 minor league pitcher of the year after posting a 10-4 record and 2.80 ERA in A and high-A as a starter. But between high-A and AA last season, he posted struggled and posted a 5.20 ERA while splitting time between starting and relieving with a 3.42 strikeout-to-walk ratio. “[My numbers] were terrible last year,” he said. “I was in the Cal League. That’s the death trap for pitchers.”

This season at Harrisburg, the Nationals wanted him to relieve. In 26 innings spread over 21 appearances, Krol posted a minuscule 0.69 ERA with a 4.14 strikeout to walk ratio. Being a reliever, he found, fit his personality better. (“I’ve never been the guy to plan out days,” he said.) He could focus on throwing harder and not worry about holding back for later innings. He could fire fastballs and not worry about mixing in offspeed pitches the next time through the order.

“The bullpen has just been a great change for me,” he said. “I can focus a lot more, not going out there and not having to focus for five, six innings at a time has helped. And I can blow it out and throw fastballs and try to throw them as hard as possible for an inning or two.”

And now, Krol has found not only a home in the bullpen but on a major league team.

“I did not know this was an option, especially this early in the season,” he said. “But I’m settling in pretty well. All the guys are great. Good support. I couldn’t ask for anything more. Just a dream come true.”