Rafael Soriano and Mike Rizzo (Jonathan Newton/The Washington Post)

Rafael Soriano stood outside the Nationals news conference room, not far from his new clubhouse, and reflected on the transformation he witnessed in Washington, a change many across baseball have noticed over the years. Soriano was a setup man and a closer with the Atlanta Braves from 2007 to 2009, a stretch during which the Nationals lost 294 games, finishing last in the National League East twice.

Soriano knew what to expect when he faced the Nationals then; much has changed since. The Nationals re-built, used two No. 1 overall draft picks to nab Stephen Strasburg and Bryce Harper, developed their players and signed key free agents such as Jayson Werth. The changes in Washington caught Soriano’s eye, in particular, last season when the New York Yankees came for a June series, and he notched two saves.

“They’re completely different from when they were in 2007 and 2008,” Soriano said in Spanish, then interrupted by a warm greeting from a team official. “They have changed 99 percent from the three years I played in this division. From last year, when I came, I saw a tremendous team, tremendous talent. I think there’s a great chance this year to win a World Series.”

With his signing, the Nationals made themselves one of the favorites to contend for a world title next season. Soriano, 33, is an experienced closer — 116 saves over the past three years — and a hard-throwing right-hander who knows how to pitch. He has been to the postseason three times: once with the Tampa Bay Rays and twice with the Yankees. Soriano is the team’s clear-cut closer now, here to solidify a bullpen that imploded in the decisive Game 5 of the NL Division Series against the St. Louis Cardinals.

The Nationals also are counting on Soriano to lend his experience to his fellow relievers, a group whose first taste of the playoffs was last season. The inexperience, the team now concedes, may have been more of a factor in last year’s postseason than they wanted to admit. Soriano, General Manager Mike Rizzo said, will help guide the other relievers.

Soriano, however, is known as a quiet person and a family man. The native Dominican can speak and understand English but is far more comfortable in his native Spanish, relying on an interpreter in his introductory press conference on Thursday. He was once given the nickname “El Silencioso” (“the Silent One”) by teammates because he would often retreat to his corner of the clubhouse to talk to his family by phone.

“I don’t really talk much,” Soriano said with a smile on Thursday. “I’m kinda quiet. One day I joke around but not all the time.”

Soriano said his demeanor wouldn’t prevent him from getting close to his teammates, and that he gets along just fine with his English-speaking teammates, too.

“I help those [bullpen] guys,” he said. “I’ve helped them a lot. Sometimes I see them doing something, and I explain to them, I tell them what’s wrong.”

When he closes, Soriano is known for quickly untucking his jersey from his pants, a tradition he started when he was with Atlanta.

“I’ve finished my job,” he said, explaining the meaning. “Like going home. I’m not trying to disrespect any batter or anyone. Just a custom.”