If the Mets and Phillies end tomorrow's games tied (~52% chance), they will play a one-game tiebreaker on Monday in Philadelphia to decide who wins the NL East. If the Padres lose Sunday's game, the loser of the Mets-Phils matchup will still have a shot at the Wild Card.
Who will the starting pitchers be in Monday's potential tilt? If both teams stay on schedule, it will be Kyle Lohse vs. Phil Humber (or maybe Mike Pelfrey). I would say that's about as bad as you can get in a do-or-die situation, but Lohse will probably get $50 million in free agency this offseason, so who knows.
Will either team throw someone else out there? I doubt it, unless Philly thinks Cole Hamels can go on two days' rest. Next in the Phils' rotation is Kyle Kendrick, and there's no point in moving him up. As for the Mets, their short-rest starter would be Pedro Martinez, and ich don't think so.
So, if the two teams fail to separate themselves tomorrow, expect a Monday slugfest.