DENVER -- Left-hander Brett Anderson, out nearly nine weeks with a broken left index finger, and righty Tyler Chatwood, out for six weeks with a strained right flexor tendon, will throw their first full bullpen sessions on Friday, when the Rockies travel to San Francisco.
There is no official timetable for their return, although speculation has Anderson coming back in early July, Chatwood after the All-Star break.
Anderson said that he and Chatwood threw 16 pitches off a mound on Tuesday; Friday's will be formal bullpen sessions.
"It helps having a guy that's on the same program as me every day," Anderson said. "He can tell you if the ball is coming out of your hand the same or coming out better. It's good to have that person, with Chatwood, day in and day out."
Thomas Harding is a reporter for MLB.com. Read his blog, Hardball in the Rockies, and follow him on Twitter @harding_at_mlb. Cody Ulm is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.