The incarceration of Chronicle reporters Lance Williams and Mark Fainaru-Wada will hobble the paper’s five-reporter investigative unit, which is already short two reporters, says Editor & Publisher online. The Chronicle’s “Enterprise Team” dates back to the 1970s Examiner, before transferring to the Chronicle when the two newspapers merged staffs in 2000. Enterprise Editor Steve Cook said two reporters are on temporary leave — Seth Rosenfeld is out until at least early 2007 on hiatus to write a book, while Erin McCormick recently began a maternity leave. That leaves veteran reporter Susan Sward, along with Fainaru-Wada and Williams, as the group’s full-timers. With a ruling Tuesday by a federal judge that Williams and Fainaru-Wada must reveal their sources in the BALCO story, or face jail, the unit’s size has moved closer to potentially becoming even smaller.