Hernandez was charged with six hits and a season-high eight runs over three-plus innings in the Mets' 13-5 loss to Atlanta on Tuesday. It was El Duque's first start since Aug. 30, and he said he had a little pain in his foot the next day.
Hernandez said Saturday it's still bothering him during his delivery, and he met with manager Willie Randolph, general manager Omar Minaya and pitching coach Rick Peterson before New York's game against Philadelphia.
"We're going to see how he feels tomorrow and then decide whether he'll pitch on Monday," Randolph said.
Hernandez got a cortisone shot for his foot after he gave up five runs and six hits over three innings at Philadelphia on Aug. 30. New York is 9-2 in his last 11 starts.
"I think we're going to err on the side of caution," Randolph said. "If there is any question or whatever then he won't pitch."
Hernandez's health could be a major question for New York as it tries to wrap up a second straight NL East title with 16 games remaining. The right-hander missed the entire postseason last year with a torn right calf muscle.
The division-leading Mets did get some good news Saturday: Backup catcher Ramon Castro was activated from the disabled list. He was sidelined for about a month with lower back arthritis.
"It surprised me," Castro said. "It was pretty bad."
Castro's return gives New York four catchers on its roster.
The Mets also recalled right-handers Joe Smith and Brian Lawrence, infielder Anderson Hernandez and outfielder David Newhan from Triple-A New Orleans.