Campbell, who broke his right collarbone on Oct. 16, just recently started throwing.
"I am up to about 30 yards now, making some improvement," Campbell told the Chronicle. "It's going good. I have only had a couple days of cardio, because when I tried to run earlier my shoulder was hurting too much from bouncing.
"It would be hard to come back this season. Could still be a little while before I am game-ready."