"He is a terrific young closer, and [he'll] make this a learning experience, be better for it in the future," Rizzo said. "Come Spring Training next year, he'll be more battle tested. The young players have grown up, and they will be veterans and know how to react to the playoff atmosphere."
With the Nationals going home, people are going to wonder what would have happened if right-hander Stephen Strasburg was not shut down. Rizzo said he doesn't have any regrets about Strasburg not being put on the playoff roster.
Strasburg was shut down in early September as part of the long-term plan to protect his right elbow, on which Tommy John surgery was performed in September 2010.
"I'm not going to think about it. We had a plan in mind," Rizzo said. "It was something that we had from the beginning. I stand by my decision. We'll take the criticism as they come. We have to do what's best for the Washington Nationals, and we think we did."
The Nats finished with the best regular-season record in baseball, but the season ended with disappointment against the Cards.
"It was a great season, but a disappointing end. I'm proud of the guys, and you have the knock the champ out," Rizzo said. "We had them on the ropes, but couldn't knock them out. It's a testament to them, but we couldn't be prouder of a bunch of our guys. It was a great season with a disappointing ending.
"The finality of these playoffs are just that. We don't know what to do tomorrow. Saturday, we don't have a game."
Rizzo declined to say what needs to improve for next season, but the Nationals have started negotiations with first baseman Adam LaRoche. The two parties have a mutual option for next year, but it appears LaRoche is looking for more than one year.
"He is great in the lineup and on the club," Rizzo said. "We've been talking and we'll continue to talk."
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.