No Premier League side has dropped more points from winning positions than Southampton this season, though, and United were back in it in the 33rd minute through Romelu Lukaku, who ended a run of 12 games without a goal for United in all competitions.
Six minutes later and Southampton were breached once again as Ander Herrera drew United level with a fine finish.
David de Gea was forced into a smart late save to preserve a point for United, who are now six points behind fourth-placed Chelsea having played a game more, while Southampton stayed in the bottom three and remained winless at home.