Fitts, who has been pitching at Triple-A Worcester, will join Boston’s taxi squad on an “if needed” basis, sources said Sunday. The Red Sox are bringing him to the West Coast as insurance because there appears to be a pitcher on the roster who is a candidate to be placed on the injured list. That, however, is a possibility and not a certainty.

The Boston Red Sox and the San Francisco Giants play the middle contest of a 3-game interleague series at Oracle Park Saturday.