Hairston is hitting just .163/.225/.398 this season after signing a two-year, $5 million contract with the Cubs in the offseason. He is coming off a 2012 season that saw him hit .263/.299/.504 with 20 homers so the Nationals will hope that he can find his form from a year ago.
Washington will likely use Hairston as a pinch-hitter. They have struggled against left-handed pitchers and Hairston can help in that respect, while also providing a veteran presence and the versatility of an outfielder who can play all three spots.
Hairston is joining the seventh team of his MLB career, but if he wants to make the playoffs for the first time, he and Washington have some work to do. The Nationals are four games behind the Atlanta Braves in the NL West and just as far back in the wild card race.