"It's good to see him square up some mistakes," manager Dan Jennings said. "He's got power to hit the ball a long way."
The Marlins have traditionally been short on left-handed power. The last lefty hitter to reach 20 home runs in a season was Logan Morrison (23) in 2011. Since Carlos Delgado had 33 homers in 2005, the next most by a lefty is 32 by Mike Jacobs in '08.
Just four times since '05 have Marlins left-handed hitters reached as many as 20 homers. Bour now has 13. A year ago, Garrett Jones reached 15.
In these final weeks, the Marlins are evaluating who fits into the plans for the future. Bour is being given a chance to see if he can become an everyday first baseman.
"He's making the most of an opportunity," Jennings said. "He's getting that chance right now. It's good to see him put good swings on the ball. He's always been a hitter, all through the Minor Leagues."
The Marlins had some chances early off Zimmermann, but weren't able to break through until Bour circled the bases in the seventh.
"Any time you go up against the Nationals, you know you're going to have to have good at-bats," Bour said. "That's a really good staff. Zimmermann did a good job of keeping us off balance. He'd go breaking ball, fastball, in and out. Had control of his pitches. We didn't take advantage of opportunities."
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.