And who now will need to prove some more. Assuming the Mets don't -- or rather can't -- trade for a top-flight starter before Spring Training, they'll enter camp with a rotation of Pedro Martinez, Maine, Perez, Orlando Hernandez and either Mike Pelfrey or Phil Humber. They'll be counting on a full season from Martinez to cancel out the loss of Glavine, simply because they have no other choice. They'll be counting on 30 healthy starts from El Duque for the same reason.
And they'll be counting on Maine and Perez to become the only starters without question marks dangling over their heads.
That's not an outlandish proposition. Both took impressive steps forward last season, and both are entering an age when starters generally hit the primes of their careers. So logic says that asking the two of them to produce more than the 30 combined victories they did a year ago would be plenty fair.
But logic doesn't always fly, and so there remains ample reason for concern. There's no guarantee that either pitcher can hang onto his gains, let alone improve upon them. And the Mets are asking for improvement. In short, they're asking for a lot.
"Just because you've had a good year doesn't mean they're going to repeat that," manager Willie Randolph said. "And they need to repeat that. They have to, because for us to be good, those guys have to step up and hold their weight. And if we don't get another pitcher, they're going to have to really step up."
The "if" is what vexes the Mets right now. They could still swing a deal for Johan Santana, or, more likely, Erik Bedard, but there's no evidence that either the Twins or Orioles, respectively, would accept what the Mets have to give. The Mets could still sign an innings-eating free agent, but quality, not quantity, is what remains in demand.
More likely, they'll stick with what they have and hope their two most durable starters can provide the fuel.
"We just have to play baseball," Perez said. "The numbers you can see after the season."
The numbers provide both encouragement and alarm. Perez often showed flashes of becoming an ace last season, but nearly as often he showed regression. And his history -- he produced two straight subpar seasons after his breakout campaign in 2004 -- makes his ability to even maintain the status quo an iffy proposition.
Maine might be the better bet to hang onto his gains, but he also can't provide any guarantees. In last season's first half, he was the closest thing the Mets had to an ace, but his season disintegrated after the All-Star break, when he won only five games the rest of the way.
"I think I let some games slip and it was my fault, whether it was preparation or whatever," Maine said. "Just learning how to pitch day in or day out, it's just something that I had to learn how to do, and hopefully it won't happen next year."
So they've learned their lessons, and grown through their pains. And now the margin for error has vanished.
Even if every starter equals his level of performance from a year ago, it will almost certainly take more than 89 wins for the Mets to recapture the National League East. And with so many age risks and uncertainties surrounding Maine and Perez on the staff, those two have to be considered the most likely candidates to make up the difference. They're the closest thing the Mets have to a guarantee, and barring a Hot Stove upgrade, the Mets will need them to be even more than that.
"I like the challenge anyways," Maine said. "To go out there and improve, that's what I want to do. I want to be better than that."
And next season, he may not have a choice.