Pagulayan, who edged unheralded Edgar Acaba, 9-7, in the second round and Leonardo Didal, 9-6, in the third, found the going tough against Gabica, a veteran campaigner, but fought back from 2-4 down by seizing five of the next six racks to wrest a 7-5 lead.
But Gabica, who bested Rolando Garcia, 9-3, Wednesday night to arrange a clash with the former world 9-ball champion, clawed his way back behind a series of spectacular shots, including one in the 14th rack that knotted the count at 7-all.
Gabica, however, came out empty on the break in the 15th rack, setting Pagulayan for a run out for the victory.
"I know I get stronger the longer the tournament gets," said Pagulayan. "You need luck to win, and I had it tonight."
Pagulayan next faces the winner between Ramil Gallego, who downed Jimmy Ching, 9-2, and Ronnie Alcano, a 9-2 winner over Bobby Petiza, which was being played at presstime.
The other two semifinalists in the winners’ group were tournament sensation Gandy Valle and Dennis Orcollo.
Valle, a gold medalist in both the 1998 Bangkok Asian Games and 2005 Manila SEAG, shocked local legend Jose Parica and Rodolfo Luat while Orcollo trounced Mario Tolentino, 9-6, Wednesday night.
Meanwhile, Leonardo Andam dropped a 7-9 decision to unheralded Victor Arpilleda to become the first big gun to fall in this six-day event staking P1 million to the champion.
Other survivors in the losers’ bracket were Nestor Ocampo, who eliminated Paquito Suarez, 9-5, Elmer Haya, who walloped Romeo del Rosario, 9-3, Lee Van Corteza, who overcame Panfilo Damu-ag, Jr., 9-2, and Roland dela Cruz, a 9-5 winner over Benjamin Guevarra, Jr.