But that certainly changed when he arrived at the University of Alabama as a freshman, when LeBlanc realized that velocity wasn't everything.
"I always thought I threw hard ... until I got to college," LeBlanc said, smiling. "That's when you learn real quickly, especially in the SEC, where your skill-set is. That's when I realized I would need something else if I was going to continue in this game."
That something else turned out to be the pitch that has placed the 23-year-old left-hander on the fast track through the Padres farm system all the way to the point where his name has popped up in conversations about the fifth starter spot in the Padres rotation.
LeBlanc's nasty changeup, a pitch the Padres as an organization covet from their Minor Leaguers, is considered so advanced that it's Major League-ready for a player who is just two years removed from being drafted.
If his career path is any indication, though, he might not stay in the Minors long. LeBlanc is 18-9 with a 2.97 ERA in his first 42 professional games (37 starts) to go with an impressive 1.09 WHIP (walks plus hits per nine innings) thus far.
Part of the reason for LeBlanc's rise through the San Diego farm system is because of the one pitch he didn't use often in high school -- the changeup.
"I had one in high school, so I wasn't completely starting from scratch," LeBlanc said. "My freshman year I started working on it. ... At some point is when it really took off."
LeBlanc, drafted in the second round in 2006, split his first professional summer with short-season Eugene and Class A Fort Wayne. He started last season at Class A Lake Elsinore, going 6-5 with a 2.64 ERA. LeBlanc then earned a promotion to Double-A, where he helped San Antonio to the Texas League title by going 7-3 with a 3.45 ERA.
"We liked what we saw of him last year in Single-A and Double-A," San Diego general manager Kevin Towers said of LeBlanc.
LeBlanc won his last four starts, posting a 1.17 ERA over 23 innings. If you include the playoffs, he was 6-0 in his final six starts with a 1.03 ERA, striking out 41 and walking nine along the way.
The changeup was certainly an important pitch, though his catcher Nick Hundley said there was much more to his success than one pitch.
"He can throw it [changeup] anytime he wants to in the count," Hundley said. "But more importantly is how he's able to locate his fastball. That sets up the pitch. When he first came up, he was more in the middle of the plate and he got hurt. When he started locating his fastball to both sides of the plate is when he became effective."
But what about that changeup?
"You see so many swings and misses at it," Hundley said. "They know that it's coming and still miss. That's how good you know it is."
As for his chances of making the rotation out of Spring Training, LeBlanc isn't getting caught up in that. He's here to get his work in, to learn from the Padres veterans in the clubhouse.
He'll likely open the season with Triple-A Portland.
"It's been fun. When first got here, it was a little intimidating," said LeBlanc, who threw a scoreless inning against Seattle on Saturday. "I've never been around these guys before and it's fun to watch them go about their business."
Corey Brock is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.