SANTA CLARA -- Tim Drevno, who's coached the 49ers offensive line with Mike Solari since 2011, will leave at season's end to become USC's offensive line coach, a league source confirmed.
Drevno is Jim Harbaugh's longest-tenured assistant, the two having coached together since 2004 at the University of San Diego before going to Stanford in 2007 and then the 49ers.
USC announced Monday night that Drevno would be joining new coach Steve Sarkisian's staff, as is former Raiders quarterback and University of Washington assistant Marques Tuiasosopo, who'll coach tight ends.
Harbaugh's staff has barely seen any turnover over the past two years.
Original members from his 2011 team are Greg Roman (offensive coordinator), Vic Fangio (defensive coordinator), Brad Seely (assistant head coach, special teams coordinator), Geep Chryst (quarterbacks), Reggie Davis (tight ends), Ed Donatell (secondary), Ejiro Evero (offensive assistant), Peter Hansen (defensive assistant), Greg Jackson (secondary assistant), Jim Leavitt (linebackers), John Morton (wide receivers) and holdovers Tom Rathman (running backs), Jim Tomsula (defensive line) and Solari, who returned to the 49ers in 2010 after an initial stint from 1992-96.
Drevno, a Cal State Fullerton product, began his coaching career at his alma mater as a graduate student before moving on to Montana State, UNLV, San Jose State (1999, offensive line) and Idaho.