The Red Sox need a roster spot so they can activate Daisuke Matsuzaka for his start against Washington in Saturday's 4:05 p.m. ET game.
Byrd was acquired in a trade with the Cubs for pitching prospect Michael Bowden on April 21, back when Boston was decimated by injuries in the outfield.
The veteran opened his time with the Red Sox with a six-game hitting streak but had cooled off since then.
With the emergence of Daniel Nava and Scott Podsednik, not to mention Adrian Gonzalez playing a little in the outfield, Byrd's role had become sparing of late.
In 34 games for the Red Sox, Byrd hit .270 with one homer, seven RBIs and a .286 on-base percentage.
He entered Friday's game as a pinch-hitter and went 0-for-1.