"(Williams) might be the front-runner," manager Willie Randolph said. "He's pitching a little better at this point."
Perez, whom the Mets received from Pittsburgh in the Xavier Nady deal, was 2-10 with the Pirates. In two starts for Norfolk, he's 0-2 with a 17.70 ERA.
Randolph would have liked to have brought back Brian Bannister (hamstring), but Bannister made a rehab appearance for Norfolk on Tuesday, so he would have been working with short rest on Saturday.
REPLAY: The Mets, whipped in the first three games of the series, unleashed the long ball Thursday to beat the Phillies 7-2 and avoid being swept.
Carlos Delgado homered twice and Carlos Beltran once to support the strong pitching of John Maine, who gave up two runs on eight hits in six innings.
2B Jose Valentin left Thursday's game with a slightly strained right hamstring and is listed as day-to-day.
CF Carlos Beltran and 1B Carlos Delgado hit back-to-back homers in the fifth inning Thursday. It was the fifth time this season the Mets have gone back-to-back, including the second time by Beltran and Delgado.
1B Carlos Delgado hit two homers Thursday, giving him 397 for his career. He moved past Joe Carter into 45th place on the all-time list.
CF Carlos Beltran tied his career-high with four hits, including his 34th homer of the season. He has 23 homers on the road this season, which leads the majors.
LF Cliff Floyd, on the disabled list with a strained left Achilles tendon, is still not ready to resume any baseball activities.
RHP Steve Trachsel (11-5, 4.84) will make his 24th start of the season Friday against Colorado. Three years ago to the day, he threw a one-hitter and beat the Rockies 1-0.
Manager Willie Randolph will choose between Triple-A LHP Dave Williams and Triple-A LHP Oliver Perez to replace RHP Pedro Martinez on Saturday against Colorado.