This is big time, people. With the Phillies up by 3 games in the National League East with 12 games to play, the Braves need to win at least two games in this series to consider a division title to be in the cards for Bobby Cox's last year as manager. This will be an especially difficult task for the tomahawking terrors, since the Phils are 19-4 since being swept by the Astros in late August, and have gained 6 games on the Braves in that time (moving from the 5th best record in the NL to the top of the heap).
The Phillies played their cards to perfection in the last week or so, lining up H20 (Roy Halladay, Cole Hamels, Roy Oswalt) to likely pitch twice each in the remaining six games with the Braves. In the last 30 days, Halladay (3-2, 4.41 ERA) has been positively average, but Hamels (4-0, 0.76 ERA) and Oswalt (5-0, 1.25 ERA) have been positively dominant, and while it's not unreasonable that their production falls back to earth a little, it would also be reasonable to think that Halladay will rise back to his normal status as well (see his Braves splits in an earlier post).
With probably the best top-3 of any rotation in baseball right now, it doesn't seem likely that the Braves could take more than 3 games from the Phillies in their remaining 6, which would result in them gaining 2 games in the division. Given how well the Phils have been hitting lately (Victorino, Utley, Ibanez, Ruiz, and Valdez all hitting over .330 in September, Howard and Werth each with 6 HR), I think that the most likely result of the remaining two series with Atlanta would be 4-2 Phillies, which would give them a 5 game cushion to deal with while facing the Nationals (who they just swept) and the Mets (who are fluttering around .500 both for the season and against the Phillies).
In order for the Braves to catch the Phillies in that event, Atlanta would have to sweep both the Nationals and Marlins and have the Phillies win at most one game against the Nats and Mets. Given that that result is a near-impossibility by most people's estimations, the Braves need to win at least four out of six games in the two series with the Phils, which would allow them to catch the Phillies with a 4-2, 2-4 (or similar combination) of records for the two teams in their other series. And after all that, the Phillies would still possibly be in position to claim the Wild Card, but I will make like the Phillies players and not concern myself with the wild card.