Crawford has been playing with pain since coming off the disabled list last month and will have Tommy John surgery.
"It became clear over last few days that surgery was going to happen," Red Sox general manager Ben Cherington said Monday on a conference call. "We felt like after talking about it more this weekend with Carl, the right thing to do is to get it taken care of now. He had played through the injury and played pretty well, but it wasn't getting better. The symptoms were getting worse. It wasn't fair to ask him to keep going out there. We decided to take care of it now and he agreed to do that."
Crawford was a major disappointment last season, his first with Boston after signing a $142-million, seven-year contract. He batted .255 with 11 home runs and 56 RBIs, and had only 18 steals after swiping 107 bases combined in the previous two seasons with Tampa Bay. He missed the first 89 games this season while recovering from left wrist surgery.
He partially tore his elbow ligament in April while rehabbing, slowing his return. Crawford was activated from the disabled list July 16 and was batting .282 with three homers and 19 RBIs.
He is expected to be sidelined six to nine months.
"The recovery is shorter than a pitcher and can be up to nine months," Cherington said. "Position players have come back sooner than that in a couple cases. It's a quicker return then a pitcher would be."