Grissom is trying to regain strength in both hamstrings before the team maps out a plan for his return, MLB.com reports.
Grissom has been running the bases and moving better, per manager Alex Cora, but a rehab assignment is not imminent. He had been expected to be Boston's primary second baseman, but Grissom may not be guaranteed that role when he's ready. The Red Sox have been getting by with lefty hitters David Hamilton and Enmanuel Valdez for now.