(Dave Tulis/AP)

Mark DeRosa, 37, serves many roles for the Nationals even though he isn’t on the playoff roster. Throughout the season, he was seen as the team dad, mentor, an additional hitting coach, team comedian and a friend. And after the Nationals dropped Game 3 and faced elimination on Thursday in Game 4 against the St. Louis Cardinals, he realized it was his chance to step in. He did something he has never done before as players prepared for the game.

He grabbed the microphone of the clubhouse speaker system that sits next to his locker, which he uses often to tease teammates and play music, and read a passage from former president Theodore Roosevelt’s famous “The Man in the Arena” speech. Since his days at the University of Pennsylvania, DeRosa would turn to those words before big games. This time, he felt he needed share them.

“With our backs against the wall, I wanted to say something that brought us together, a little band of brothers to go out and fight and see what happens,” he said. “I feel that was fitting.”

Players who weren’t in the clubhouse came streaming in. Jayson Werth, an early advocate for mascot Teddy to win the Presidents Race at Nationals home games, darted into the room to listen. Others did, too. Inspiration filled the room, players said.

“Epic,” Drew Storen said. “The stuff movies are made of.”

DeRosa felt that his teammates, composed mainly of young players new to this stage, needed to hear something. Nationals Manager Davey Johnson isn’t one for team meetings or gatherings, leaving the clubhouse to the veteran players. So once DeRosa grabbed the microphone, the players stopped to listen.

“Coming from a guy like that, who everybody has so much respect for and has been in the postseason, a lot of time it’s joking but a lot of it is serious, too,” Adam LaRoche said. “Kind of keep the humor going but also pump guys up. He’s going to make a great manager one day.”

DeRosa, who won a World Series with the San Francisco Giants in 2010, dealt with much this season: injuries that forced him to miss long stretches of the season and the death of his father. The Nationals signed DeRosa in the offseason because of his versatility in the field and veteran presence. He fully understands and relishes his role as being more important to his teammates off the field.

“I feel like if they’re going to keep me around and keep me here, there’s a reason for it,” DeRosa said. “So I’ve been in these games. I’ve grinded with guys. I’ve been on that team. I know how [Yadier Molina] thinks. I know how [Chris Carpenter] and those guys think in playing with them. If I can bounce anything off them, down to remembering the bunt signs, just stupid stuff. Sometimes guys don’t always want to go to coaches, they’d rather come to a player and work them through an at-bat.”

DeRosa read part of the speech Thursday, but added some colorful flair, as he always does, before and after.

“I think he dropped a couple F-bombs,” Tyler Clippard said. “That was fun. … He was reading right off the page. It sounded awesome.”

Added DeRosa: “I went about it the same way I always do except I wanted to be a little less funny and a little more serious. They won’t listen to it if I don’t throw a few jokes in there.”

DeRosa didn’t pick Roosevelt’s speech because of the tie to mascot Teddy. It’s a speech he has leaned on much of his career. But it was a fitting coincidence, he said.

“It’s perfect,” he said. “The guy is like 3-0. Or 3-800. After I read that, [I said], ‘You know who spoke these words? Teddy F-ing Roosevelt.’”