West Ham suffered more jitters against Astra Giurgiu as they were held to a 1-1 draw in the first leg of their Europa League playoff on Thursday.
The Hammers, bidding to reach the group stages for the first time, looked set to take a 1-0 lead back to the London Stadium next week thanks to Mark Noble's penalty on the stroke of half-time.
However, Romanian champions Astra, who beat Slaven Bilic's side in last season's qualifiers, stunned the visitors again when sub Denis Alibec hit a late equaliser.
Southampton will face Dutch club Vitesse Arnhem in the third qualifying round of the Europa League, while West Ham were handed a potential tie against Scottish Premiership side Inverness Caledonian Thistle should they both progress.
Saints finished seventh in the Premier League last season and so were among the sides for Friday's draw in Nyon, Switzerland.
The fixture will see Southampton manager Ronald Koeman return to the Netherlands, where he previously managed Vitesse before moving to England.