Heineman (hamstring) began a rehab assignment Saturday with Double-A Portland and went 1-for-3 with a run and an RBI while serving as a designated hitter.
On the 10-day injured list since April 23 with a right hamstring strain, Heineman will likely need to make multiple starts at catcher during his rehab assignment before he's activated. Heineman still has one minor-league option remaining, so he could eventually settle at Triple-A Worcester once activated if both of the Red Sox's top two backstops (Connor Wong and Reese McGuire) are both healthy.