The Mets are running out of healthy pitchers at the worst possible time.

Already missing Pedro Martinez, the NL East champions suddenly might have to replace scheduled starter Orlando Hernandez in Game 1 of the playoffs because of a calf injury, too.

El Duque felt discomfort in his right leg while he was jogging in the outfield yesterday as the Mets tuned up for their first-round series against the Los Angeles Dodgers. The 40-year-old right-hander was pulled off the field and went for an MRI exam.

“Obviously, we’re up in the air on who’s our starter tomorrow,” the Mets’ manager, Willie Randolph, said. “We have some options, obviously, but we’ll wait and see how he feels first and then we’ll make a decision.”

Those options are limited, however. Martinez, a three-time Cy Young Award winner, is out until next summer because of calf and shoulder injuries.

Tom Glavine, slated to start Game 2, pitched Saturday in Washington. So if the Mets want to bump him up, the 40-year-old lefty would be working on only three days’ rest.

Steve Trachsel, who went 15–8 with a 4.97 ERA this year, skipped his scheduled outing last weekend to attend to a family matter on the West Coast. He was due back in New York yesterday, but Randolph said the right-hander probably wasn’t an option to pitch today in Game 1 on such short notice.

Randolph didn’t even think Trachsel had been throwing while he was away from the team.

That left rookie right-hander John Maine as a possibility. Maine was 6–5 with a 3.60 ERA in 16 games this season, including 15 starts.

But he obviously lacks the October experience the Mets were counting on with Hernandez, acquired from Arizona in May. El Duque is 9–3 with a 2.55 ERA in 19 career postseason games, including 14 starts, mostly with the Yankees. He also owns four World Series rings, and his teams are 12–3 in postseason series.

Hernandez’s MRI showed an injury to his calf, the Mets said — but they wouldn’t provide further details.

Doctors were to re-evaluate the test results last night, and the Mets planned to wait and see how Hernandez feels when he wakes up today before deciding on a starter. They must submit their 25-man roster for the first round by 10 a.m. today.

“It’s not great news, that’s for sure,” Randolph said. “He was very upset.”

As for the Dodgers, their rotation is all set for the first three games. Derek Lowe will go in the opener, followed by rookie left-hander Hong-Chih Kuo and future Hall of Famer Greg Maddux, who has 333 career wins.

Lowe pitched his best ball of the season down the stretch, going 8–1 with a 2.39 ERA in his final 11 starts to help Los Angeles win the NL wild card.