"I don't know if I want to go into all the reasons," manager Don Mattingly said. "We feel this is the best club with St. Louis for where we are right now, the way the roster sets up with the number of players we're keeping. We met for five hours. There are all kinds of different reasons."
The decisions were necessitated because, despite aggressively going after power right-handers like Marmol and Volquez, the Dodgers trusted Rodriguez for the pennant race and didn't add any lefty relievers. They tried youngster Onelki Garcia in September, but he wasn't ready.
The moves leave the Dodgers with J.P. Howell as the only left-handed reliever to go with six right-handers: Marmol, Volquez, Kenley Jansen, Brian Wilson, Ronald Belisario and Chris Withrow.
"It was a tough decision for a guy that helped get us to this point," Mattingly said of Rodriguez. "But people that followed us the past five or six weeks know it's really been two different guys before that point and after. He got to be a little different. Was it from usage? In his first full year, did he run out of gas? Whatever it is, it didn't make it any easier."
Rodriguez didn't sound surprised.
"It's their decision," Rodriguez said after he heard the news. "Of course I wouldn't be happy if I don't make it. I understand we're trying to win. That's the most important thing. If I'm off the roster, I just have to keep my head up. No point in getting down."
Rodriguez made 76 regular-season appearances, and he was lights-out the first five months of the year, before fading slightly in September. The slump continued through the NL Division Series, when he allowed left-handed hitter Jason Heyward a two-run homer and a two-run single.
"I just haven't been executing, leaving the ball in the zone," Rodriguez said. All week I've been working on that, getting the ball down in the zone."
Marmol, acquired from the Cubs in a trade for Matt Guerrier, showed significant mechanical improvement upon joining the Dodgers, posting a 2.53 ERA and 27 strikeouts in 21 1/3 innings. The former All-Star closer walked 19. He got the nod over another former All-Star closer, Brandon League, who started this season as the Dodgers' closer, but lost the job to Jansen.
"Carlos has really good numbers against [the Cardinals], and he's been good for us against lefties and righties," said Mattingly.
Volquez, almost exclusively a starter throughout his career, will replace Capuano as the long reliever. Capuano, kept on the NLDS roster because of concerns over Hyun-Jin Ryu's health, made that decision look brilliant when he took over after Ryu's three-inning start in Game 3 and pitched three hitless frames. The Dodgers rallied and eventually won the pivotal contest. But Capuano allowed five runs in five innings in a May 24 start against St. Louis, and he is considered a bad matchup against the Cardinals' right-handed hitters.
Capuano, who was gracious all season despite bouncing in and out of the rotation, took the high road again.
"I think Donnie had the enviable problem of having a lot of good options," he said. "He said they went through the numbers, and he was going to take me off the roster. He had a lot of good arms in the holster, and somebody had to come off."
Capuano dismissed the notion that he might be hurt, either with the groin strain he suffered in September or another injury.
"I've been feeling great and throwing well," he said. "We all know we have guys that were not on the roster last time -- Peter Moylan, Brandon League, Carlos Marmol and Edinson Volquez -- all solid pitchers. It's a numbers game, and that's how it goes."
Capuano said he hadn't been "focused too much" on whether he was on the roster bubble. But he also said he looked at video of himself facing the Cardinals over the last three years and "didn't notice anything glaring."
Volquez made five starts and one relief appearance for the Dodgers in 2013, who signed him after he was released by San Diego. He had a 5.97 ERA with the Padres, which he lowered to 4.18 with the Dodgers after some mechanical tinkering.
Marmol and Volquez are in a group of seven Dodgers that were not on the NLDS roster, but they continued to work out with the club, including throwing regular bullpen sessions. The others were pitchers League and Moylan, infielder Jerry Hairston, catcher Drew Butera and outfielder Nick Buss.
Although Andre Ethier started in the outfield Friday night, speedster Dee Gordon remained on the roster for pinch-running purposes because of uncertainty over Ethier's baserunning ability. That closed the door on Hairston, a 15-year veteran with postseason experience with the 2011 Brewers and the World Series champion 2009 Yankees.
Michael Young, acquired at the Aug. 31 waiver Trade Deadline, continues to back up Mark Ellis at second base and Juan Uribe at third base.
The Dodgers will again carry 11 pitchers and 14 position players.
Any injured player can be replaced during a series, but that player becomes ineligible for the next series.
Rosters can be changed for the best-of-seven World Series.
Here is the 25-man roster:
Starting pitchers: Clayton Kershaw, Zack Greinke, Ryu, Ricky Nolasco.
Bullpen: Jansen, Wilson, Belisario, Marmol, Howell, Withrow, Volquez.
Catchers: A.J. Ellis, Tim Federowicz.
Infielders: Adrian Gonzalez, Ellis, Hanley Ramirez, Uribe, Nick Punto, Young, Gordon.
Outfielders: Carl Crawford, Skip Schumaker, Yasiel Puig, Scott Van Slyke, Ethier.