Which is a very real concern. Still, if they're not able to lock up Perez (which looks likely, as everything I've read points to him testing the free agent market after this year), they'd still have three respectable starters (I'm holding out hope that Pelfrey can pass for a number five by then). Given the amount of pitching talent available in next year's off-season, it'll be expensive but not impossible to maintain a solid rotation.