The Red Sox reinstated Grissom (hamstring) from the 10-day injured list Thursday and optioned him to Triple-A Worcester, Julian McWilliams of The Boston Globe reports.
Grissom has taken a massive step back at the plate in the big leagues this year, slashing just .148/.207/.160 with three RBI in 87 plate appearances. He's begun to rediscover his swing while on a rehab assignment with Worcester, tallying a hit in nine of his last 10 games, but the Red Sox will keep him stashed away in the minors now that he's fully recovered from his right hamstring strain.