WASHINGTON -- The Cardinals have seemingly no issue thrusting three rookie relievers into the pressure cooker that is the National League Division Series. All things considered, they've been pitching in such situations for weeks now.

With the addition of Shelby Miller to the postseason roster -- in place of starter Jaime Garcia, who was shut down Tuesday with a left rotator cuff strain -- the Cardinals now have three rookies out of the bullpen in Miller, Joe Kelly and Trevor Rosenthal.

"It's been nice," fellow reliever Mitchell Boggs said. "It's been impressive. They've been brought up this year and put into a playoff race and all three of them have pitched outstanding. It's exciting to see these guys come into this situation and thrive and know that we can run them out there in tough situations and none of them are gonna back down."

Rosenthal credits St. Louis' more prominent and experienced relievers like Boggs and closer Jason Motte for helping usher in the new trio, which has combined for a 6-9 record with a 3.20 ERA in 49 total appearances this season.

"I think we all just view it as a tremendous opportunity," said Rosenthal, who had a 2.78 ERA in 19 appearances in the regular season. "This is what we always dreamed of being able to do, being at this level and in the postseason. It's a great feeling for each one of us and to experience that together.

"We're all new to this, and to go through that ride together, to experience it, learn from each other and the other guys ... one day, all of three of us could be together and setting the example for some guys that are in the shoes that we are now."

Both Kelly, who was 5-7 with a 3.53 ERA in 24 appearances (16 starts) and Rosenthal logged important innings in St. Louis' Game 2 victory on Monday at Busch Stadium. Kelly threw a perfect sixth, while Rosenthal struck out three, while allowing one hit in a scoreless ninth.

"I think a lot of it has to do with the pressure we put on these guys down the stretch," Cardinals manager Mike Matheny said. "Every game to us was a playoff-style intensity, where it seemed like every game, everything was on the line. We weren't afraid to go to our young guys in high-leverage situations, so they have proven the fact that they are ready to pitch. Now it's just getting the repetitions."

Miller gets the call to replace Garcia on roster

WASHINGTON -- When the Cardinals' National League Division Series roster was announced, Shelby Miller was left off. But he didn't go far. Miller stayed with the team, so when he was needed again before Wednesday's Game 3 against the Nationals, he was ready to jump back in the mix.

It's just another first for the young right-hander, who joined St. Louis' postseason roster on Tuesday after the club shut down starter Jaime Garcia with a left rotator cuff strain and inflammation.

"It's nerve-racking right now to think about it," Miller said. "Right now, it's gonna be a tough spot for me, as far as what I'm going to do. You never really know out of the 'pen. I'm just looking forward to the opportunity. I'm really excited about it."

With Garcia out of the rotation, Lance Lynn would likely slide back in, though he threw 50 pitches on Monday and probably wouldn't be available unless the Cardinals advance past the NLDS. Miller, 1-0 with a 1.32 ERA in 13 1/2 innings this season, now gives the club another long man out of the bullpen.

"With this roster against the Nationals, we felt like we have more of a need with potentially a pitcher that could go a long ways, especially after we just took Lance Lynn out by him throwing the amount pitches that he threw yesterday," Cardinals manager Mike Matheny said. "We would need multiple innings, and we would need a guy who has worked up to that, and that would be Shelby at this time."

Miller, ranked by MLB.com as the Cardinals' No. 2 prospect, made his debut on Sept. 5 out of the bullpen in St. Louis' 6-2 loss to the Mets. His last outing of the season, on Oct. 3 against the Reds, was his only start. He tossed six innings of one-hit ball, taking a no-hitter into the sixth. But he was left off the initial postseason roster.

"It's my first time up here in the big leagues," Miller said. "Obviously, when I didn't make the roster, traveling with the team, maybe there was a possibility I'd pitch, but the odds weren't great. So it's crazy that I'm on it now. It's definitely going to be a lot of fun. Hopefully I get in there and pitch and help the team win."

Miller has not faced the Nationals this season, but did pitch against Washington in two Spring Training starts. In 4 1/3 innings, he allowed four earned runs on six hits, including two home runs, for an 8.31 ERA.

"We've got all the guys, all the film, and all the veteran guys have been around," Miller said. "We've got [Yadier Molina] catching, and the main thing for me is to just follow him. He knows the hitters real well, he's been around the game for a long time, so I just follow whatever he calls. Even if it's a pitch I'm not comfortable with, I'm gonna throw it. I trust him 100 percent."