Olivier Giroud led by example as his brace from the bench helped Chelsea come from behind to deepen Southampton's relegation fears.
The Frenchman replaced Alvaro Morata midway through the second half with the Blues down 2-0 but a header and a low strike, coupled with a smart finish from Eden Hazard ensured an away victory.
Southampton were aiming for their first Premier League win under new boss Mark Hughes and looked on course after goals from Dusan Tadic and Jan Bednarek only to suffer a late collapse.
More to follow.