"We wanted to wait until [Friday]," La Russa said on Saturday. "Chris played catch and passed the test, so if we play tomorrow, Chris starts."
Carpenter did not throw a bullpen session on Friday, in anticipation of possibly receiving this assignment. Instead he only threw lightly during the team's brief workout.
"I just waited," he said. "There wasn't really any preparation, especially very much of a rest knowing I'm not going to do my normal lifting routine between [starts]. I just waited to hear what they had to say."
If the game were not an elimination game for the Cardinals, it's likely that either John Smoltz or Kyle Lohse would have gotten the call to start. However, the Cardinals must win all three remaining games in the series in order to advance to the National League Championship Series.
Carpenter had a very difficult start in the opener of the NLDS, allowing four runs in five innings and needing 105 pitches to get 15 outs. La Russa said, however, that Carpenter's slog did not deter him from going with his ace and former Cy Young Award winner on short rest. And of course Carpenter expressed no reservations.
LONG ODDS ON SHORT REST
"It was definitely a battle, but I think any playoff game is going to be a battle," Carpenter said. "There's no easy pitches in a playoff game. They're all grinding. What [have] we got to lose? It's going out there and trying to do the best you can and give your team a chance to win."
Pitching Carpenter on Sunday also allows the Cardinals to pitch Adam Wainwright on regular rest on Tuesday if the series goes to a fifth game in Los Angeles.
"If we were playing on Monday, Game 5, we wouldn't do it," La Russa said. "Because then you'd have to pitch him and Adam both [on short rest]. But ... there is an off-day Monday and Adam will be fully rested. It's an edge that you play. It's fair to say that we're always careful with our pitching, and careful with Chris, and we'll be extra careful. [We just want him to pitch] as hard as he can, as long as he can. If that's five innings, six innings, fine. Whatever he's got, it helps us compete in that game."
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.