The 25-year-old left-hander allowed a run on six hits over eight-plus innings Wednesday night as the Triple-A Knights shut down the Indianapolis Indians, 8-1.
"It was good, it was one of my better starts," Leesman said. "It was the longest start of my career. I went eight innings and came back out for the ninth. I couldn't get the 'CG,' but we were good in every aspect. We had great defense, great offense and great pitching."
The White Sox's No. 10 prospect gave up a run in the opening inning on consecutive singles and Hector Luna's RBI groundout. But he set down 15 of the next 16 batters, then stranded two runners in scoring position in the seventh and retired the side in order in the eighth.
Having thrown 102 pitches, he came back out for the ninth but was pulled after Chase d'Arnaud beat out an infield single and Luna flared a ball into shallow left field.
"I heard I was over 100 pitches after eight, but they wanted to see if I could get it done. I was on a pretty short leash," Leesman said. "There was a close play at first and a broken-bat single. It was unfortunate, but it was a good start."
The Xavier University product relied primarily on his fastball-slider combination, occasionally mixing in changeups later in the game to keep the Indians off-balance.
His game plan didn't deviate too much from the regular season, nor did his mind-set.
"I didn't feel any more pressure," the 25-year-old explained. "It's the same, whether it's the World Series or Rookie ball. I take everything as serious as the next. For me, the first game of the season vs. the playoffs, I take that first game just as serious. Every start is a new game for me."
Leesman, a 2008 11th-round Draft pick, got plenty of offensive support. Seth Loman smacked a two-run homer, reached base five times and fell a triple short of hitting for the cycle. Brent Morel contributed two hits, including an RBI double, No. 16 prospect Jared Mitchell went 3-for-5 with a triple and Josh Phegley homered.
"[Loman] was great. To see him put up two runs in his first at-bat, that set the tempo for the game. Getting three runs in the first inning helped me get comfortable -- but not too comfortable -- and it made my job easier," Leesman said.
"Everybody was great: Phegley with a home run and Mitchell with three hits. One through nine, they're all good hitters. We have total confidence. You can ask anybody on this team and they will tell you the same thing."
In other International League action:
Pawtucket 7, Scranton Wilkes-Barre 4
The Red Sox rallied from an early deficit, scoring seven unanswered runs to take the first game of the other best-of-5 semifinal.
J.C. Linares, Andy LaRoche and Bryce Brentz homered, while Tony Thomas went 3-for-4 with a pair of doubles and two runs scored for Pawtucket.
PawSox starter Zach Stewart (1-0) recorded the win, despite allowing four runs on seven hits and two walks over five innings.
Kevin Russo and Luke Murton homered for the Yankees. Gameday box score