If there is going to be a “book” on how to pitch to Bryce Harper in professional baseball, Jason Gurka may be one of its authors. On Monday night, Gurka, a left-handed reliever for the low Class A Delmarva Shorebirds — a Baltimore Orioles affiliate — faced Harper twice, and struck him out both times on curveballs out of the strike zone.

In today’s paper, I wrote about Harper’s offensive tear through the South Atlantic League and describe some of his adventures in the other aspects of the game. What I didn’t have room to get into was the occasional difficulty Harper, the Washington Nationals’ right field phenom, has had at the plate when facing lefties with good breaking balls.

“Difficulty,” of course, is a relative term: His OPS against lefties this year is “only” 1.016, as opposed to 1.279 against right-handers. Harper is likely the best hitting prospect in decades, maybe the best ever. But I have watched him enough times by now to know he can be pitched to, particularly if you are a lefty with a quality breaking ball who can hit your spots. There are few of those, of course, in the Sally League, but it will be something to watch as he moves on to higher levels, where the pitching will be uniformly better.

“He’s going to do damage with the bat no matter where he goes,” said a scout from an American League team who also saw Harper this week. “He could probably go to [Class AA] Harrisburg and at least be dangerous enough, often enough to justify it. But he has holes in his approach and his swing that, as he goes up further, pitchers are more capable of attacking.”

After Gurka’s double-takedown of Harper, I sought out the 23-year-old Texan — who has had a fairly undistinguished minor league career to this point — to discuss the way he pitched the phenom (whom he had never faced before), and the conversation was enlightening. Here is part of it:

You clearly had an idea of how to pitch Harper, and the strategy seemed to be to get him to chase breaking balls out of the zone late in the count. Is that right?

Gurka: “We knew he’s a little bit of a free swinger. He goes up there to hack. You just have to make sure you don’t miss your spots because he’ll hurt you. But I kind of feel like you can get him outside, because it seems like he wants to pull it. And you might be able to get him to chase a breaking ball in the dirt.”

You also threw some quality fastballs during those two at-bats.

Gurka: “Yeah, the first time, I challenged him with a first-pitch fastball. He’s a first-pitch swinger, so I threw my best fastball on the outside corner [Harper swung and missed] and painted it where I wanted it. I also jammed him with an inside fastball in the second at-bat. [Harper fouled it away.] If you go inside, you have to be perfect, maybe even a little off the plate. Because if you miss and catch the plate, he’ll hurt you.”

How much tougher would he be to pitch to if he had more plate discipline?

Gurka: “If he was a little more patient and watched some pitches, it would be a little tougher. Those curveballs in the dirt, if he watches those — I mean, what do you do then? He’s still young, still learning. But you know he’s going to be a great hitter.”

The main question I had for folks in Hagerstown was this: Given his gaudy numbers, was Harper still being challenged enough by facing Sally League pitchers to justify his remaining there?

Here was the answer of Marlon Anderson, the Suns’ hitting coach, to that question: “He’s definitely still being challenged, no doubt about it. Think about that curveball down and away that he chases sometimes. It’s about patience, and he might struggle with that for awhile.”

I even posed the question to Harper himself — in a sense, to challenge him in a different way. I thought his answer was a 500-foot homer.

“Definitely,” Harper said. “Look at [Gurka]. That guy came in and got me twice. I tip my cap to him. But I felt good up there. I felt like I could hit those balls a mile. I don’t want to say I’m better than everybody. I don’t want to say I should go to the next level right now. I’m not going to say I should be in the big leagues right now. Because there’s so much I need to learn. I need to get a feel for this.

“You have to learn the game. I didn’t want to be here out of spring training. But once I got going and was around the guys I needed to be around, and started getting out here for early work . . . The work I’m doing in the outfield is huge; they want me to make an impact [in the majors] right when I get there. So I’m trying to get better every day.”