The Nationals waived Moore and outrighted him off the 40-man roster to Triple-A Syracuse earlier in the week. Moore has played in 277 games for Washington over the past four seasons.
Moore, a 29-year-old outfielder who can also play first base, has hit .228 in his major league career.
Freiman, who's 6-foot-8, last appeared in the majors in 2014 with the Oakland Athletics. The 29-year-old hit .256 in 301 plate appearances for Oakland.