Tony La Russa waffled and finally decided to start Chris Carpenter tonight on full rest, allowing him to pitch game 6, also on full rest. Without the rainout Wednesday, Carpenter would have been forced to start games 3 and 7 unless he went on three days' rest. The talking heads on Fox and ESPN are discussing how the rainout helped the Cardinals by allowing them to move Carpenter up in the rotation.
The rainout was a Greek gift. Carpenter should have remained on schedule to pitch in games 3 and 7. By using him in games 2 and 6, they've all but eliminated the chance he can start three games in the World Series, a change which would have improved their chances of winning the WS by about 4% if they had won the NLCS in 5 or 6 games. Moving Carpenter up, in contrast, increases the chance of winning the NLCS by a paltry 0.4%. The result is a net loss of 0.4% to the Cardinals' WS title hopes, a significant hit when their total chances are under 12%.
You'll probably hear, or have heard, a lot of talk of momentum and how teams rarely come back from 2-0 deficits, so the Cards need to put Carpenter in now to avoid the 2-0 hole. Obviously, teams in 2-0 holes will rarely come back to win. If the teams are evenly matched, the team down 2-0 will need to win four of the next five games. There are 32 possible outcomes of a five-game series, assuming they continue playing even after one team has clinched. Out of these, the team in the 0-2 hole will win four or five only 6 times, so they are more than a 4-1 dog. Historically, teams in an 0-2 hole have performed in line with these numbers. As Fox displayed in a graphic during today's ALCS game, plenty of teams have come back from 0-2 deficits. It is not the end of the world.
Hypothetically, let's say the Cardinals automatically win Carpenter's start and lose Suppan's. After game 3, is there any additional value in having won game 2 instead of game 3 if you're down 2-1 either way? If anything, wouldn't you rather have the "momentum" of having won your last game? Furthermore, an extra day of rest is more likely to help Carpenter, who has tired down the stretch, than Suppan, who has pitched much better in the second half.
Moving Carpenter up wasn't extremely costly, but the Cardinals can't afford any slip-ups at this point.