The former closer, who was with the organization in Montreal from 2003-04 and Washington from 2005-08 before his career ended with the Mariners in 2010, holds the franchise record for saves in a season (47 in 2005).
"It's just kind of weird putting on a Nationals jersey in general, but it's cool to be back here and doing it," Cordero said. "I never thought I'd be able to come back here and throw out the first pitch."
Cordero made just six appearances in the 2008 season because of a shoulder injury that essentially ended his career. He signed a Minor League deal with the Mariners in 2010, but he made nine appearances before retiring officially the following year.
At 30, he said the time away from the game has him itching to get back.
"I want to go out there and play again," Cordero said, adding that he'll try to play winter ball this year. "It's still real hard to watch baseball, but I still do, because I'm a fan of the game. But I want to get out there and throw again."
He threw out the first pitch Friday to reliever Drew Storen, who last year came within four saves of tying Cordero's season saves record.
"I took a huge sigh of relief [when Storen didn't get it]," Cordero joked. "But I think he'll get it one day, whether it's next year or the year after. I think he'll definitely get my 47 saves here, and it'll be a sad day when he does. But at the same time, it'll be really cool."
Cordero, an All-Star in 2005 when the Nationals moved back to Washington, looked back fondly on that first season in D.C., but he said this year's squad has the opportunity to take it one step further.
"Hopefully this is the year the town of D.C. gets to see a playoff here," Cordero said. "We tried to give it to them that first year. That first year was magical. Coming from Montreal, playing at RFK Stadium, being in a city that hadn't had baseball in about 30 years. We played very well, but unfortunately took a dive in the second half.
"But this team, I don't think they're going to do that. They have the pitching staff to go out there and make it all the way to the World Series."