The Red Sox designated Heineman for assignment Saturday, Chris Cotillo of MassLive.com reports.
Heineman has been in the minors since June 24, where he has since slashed .262/.375/.492 with four homers and 11 RBI across 73 plate appearances. Despite his solid performance, he'll be stripped of his spot on the 40-man roster in favor of Zach Penrod, who was selected from Triple-A Worcester in a corresponding move.