Dunn said he has had problems with the wrist for a while, but the pain grew worse against the Red Sox after fouling off a pitch in the fourth inning on Tuesday.
"It's a precautionary thing. ... It's no big deal," Dunn said. "I don't want to get days off. I don't feel like I do. You [can] just call it a good solid benching."
With Dunn on the bench, manager Manny Acta put Josh Willingham in left field and inserted first baseman Nick Johnson as the cleanup hitter. Outside of Dunn, Johnson is the one guy who can protect Ryan Zimmerman in the lineup, said Acta.
Roger Bernadina, on the disabled list because of a fractured right ankle, played catch with head athletic trainer Lee Kuntz and didn't have any problems moving his legs. Bernadina acknowledged that the ankle is still sore and will have X-rays in a couple of weeks. He hopes to return in the big leagues sometime in September.
Southpaw Matt Chico, on the DL because of left elbow reconstruction surgery, had a bullpen session on Wednesday. He didn't have any problems throwing all of his pitches.
Chico is scheduled to pitch three innings for Double-A Harrisburg on Saturday.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.