Kucewicz, the squad's No. 2 hitter, was out with strep throat, and DeLeo was not available because of a school-related issue.
"I told the guys, 'We're going to live for another day,' " Golden Panthers assistant coach Kevin O'Brien said. "We wanted to give the guys who weren't here a chance to play again."
The fourth-seeded Golden Panthers (17-6) will face top-seeded and defending champion Holy Ghost Prep in a semifinal at 4 p.m. Thursday in Bensalem.
Against the fifth-seeded Golden Bears, who last season placed second in districts and advanced to the state final, Lafferty struck out nine and walked two. He mixed a fastball, slider, and change-up.
"I threw a lot of sliders, everywhere in the count, and tried to get ahead of hitters," said the 6-foot-3, 190-pounder, who will continue his career at Widener.
After giving up three consecutive hits and two runs in the fourth inning, Lafferty fanned five of the next seven batters. Upper Moreland (12-7) added an unearned run in the seventh. Lafferty missed most of last season because of elbow tendinitis.
"He kept us off balance," Golden Bears coach Ernie Rehr said. "He never gave us an opportunity to control the game. We had a couple of sharp hits, but couldn't string anything together."
Pope John Paul centerfielder Kyle Miller (3 for 3, three RBIs) highlighted a five-run fifth inning with a two-run single to center.
"This is the best day he's had hitting all year," O'Brien said.
Also chipping in were shortstop and Lehigh recruit James Bleming (2 for 4, solo home run) and leftfielder Joe Pedorenko (2 for 4). Rightfielder Evan Myers and third baseman Andrew Szpindor had RBI singles.
Upper Moreland 000 200 1 - 3 5 2
Pope John Paul II 010 151 x - 8 12 3
WP: Josh Lafferty. LP: Eddie Decker. 2B: UM-Charlie Hooker. HR: PJP-James Bleming.