"Guys get caught up in pitching to a hitter's weakness if they find out he can't hit a certain pitch," the hurler says. "But if you can't throw the pitch well that he can't hit, then I think you're wasting your time trying to throw it."
Johnston adds that this policy does not mean neglecting a hitter's weakness altogether.
"If you're up 0-2 in the count, throw an outside pitch," he advises. "If you miss outside, it's not a big deal. But I don't like to go after a guy's weakness a lot if it's not the pitch I'm comfortable thowing on a given day."
The Berlin, Conn.-native says he "started to become the pitcher he wanted to become" during his senior year at Berlin High School. After seriously working out for the first time in the off-season, he returned to make the all-state team.
But things haven't always gone smoothly. During his sophomore year at Harvard, Johston experienced "possibly the worst baseball day" of his life.
In the last inning of the first game of a doubleheader against Boston College, Johnston was called upon to work the Crimson out of a bases loaded jam.
He gave up a grand slam.
Then Johnston, the scheduled starter, had to take the mound in the second game.
The first pitch he threw resulted in a freak line drive off the elbow of his pitching arm. Johnston was sidelined for three weeks.
"Those were two of the successive worst pitches I've ever thrown in my life," Johnston remembers.
The senior can joke about the incident now, but the comeback trail was long. It included a rocky junior year when he went 1-6, despite a respectable 3.31 ERA.
Last summer, Johnston participated in the Great Lakes League, an organization jointly funded by the NCAA and Major League Baseball for amateur talent.
He shone, going 5-3 and starting the All-Star game. He also led his team, the Columbus, Ohio All-Americans, to the championship game an recorded the win, 7-6.
"That was one of the best baseball experiences I've ever had," Johnston says.
Now that his Harvard years are over, Johnston is looking toward the major.
His best pitches, the fastball and the splitfingered fastball, have been clocked as high as 88 miles per hour, and the New York Yankees and Chicago White Sox have shown an interest in him.
"It would hurt a little bit to spend this much time working at it and not get a chance to play pro-ball," Johnston says.
"Dan, Jim, [left-fielder] Nick [DelVecchio] and I all feel the same way. Those guys were down there taking batting practice on their own all year long," the pitcher says. "For any of the four of us not to get a shot would be kind of heartbreaking."