The Nationals have been looking for a first baseman since they allowed slugger Adam Dunn to become a free agent. LaRoche, 31, brings consistency with both the bat and glove. He is coming off the best season of his career, hitting .261 with 25 home runs and 100 RBIs for the D-backs. He is also an above-average defensive first baseman.
This offseason, Washington has put an emphasis on defense, which has been below average the last three years. Members of the Nationals' front office privately said that Dunn was not good enough to play the position.
LaRoche will be reunited with center fielder Nyjer Morgan and reliever Sean Burnett. They were teammates for more than two seasons from 2007-09 in the Pirates' organization.
Both Morgan and Burnett said that adding LaRoche is a great move because he brings leadership and will improve the team's defense.
"He is a very laid-back guy, but at the same time, he will bring a veteran leadership presence in the clubhouse," Burnett said. "He has one of the sweetest left-handed swings in the game right now. He has a lot of power and is one of the best defensive first basemen in the league.
"People don't know how good he is defensively. He is a Gold Glove-caliber first baseman. He is second to none. I played with him in Pittsburgh. He is as good as they come. He has shortstop hands as a first baseman. It had a huge impact on the pitching staff. He makes plays that you don't expect other people to make."
Said Morgan: "Oh, man. He is a good guy and a true leader. He fields his position. He brings positive energy. It's something that we need for [next season]. We have to clean it up on defense. That's what we have to do to get to the next level."
LaRoche has played in the big leagues for seven seasons. He is best known for playing with the Braves, but he has also spent time with the Red Sox. During those seven years, LaRoche is a .271 career hitter, with 161 home runs and 569 RBIs.
He is one of just five big leaguers to have hit 20-plus home runs as a first baseman each of the last six seasons. He is joined on this list by Albert Pujols, Mark Teixeira, Paul Konerko and Ryan Howard. LaRoche has also legged out 30 or more doubles five straight years.
LaRoche comes from a baseball family. His father, Dave, was a solid relief pitcher for the Angels, Yankees and Indians in the 1970s and '80s, while his brother, Andy, played third base for the Pirates the last three years before becoming a free agent.
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.