West Ham had their goalkeeper Adrián red carded and sent off with half an hour remaining, but unsatisfied Southampton only managed a bore draw at St Mary's.
Southampton hoped for a seventh win in nine league matches and introduced new on-loan signing from Benfica, Filip Djuricic, 23 but neither he nor fellow Serbian compatriot Dusan Tadic, 26, could break the claret and blue resistance.
Adrián, the West Ham keeper, was untroubled until around the hour mark, when Mané run and shot prompted Carl Jenkinson, 23 to make a clearance, before the first sending off of the Spanish goalkeeper's career arrived.
Adrián was red carded, as his effort to wrong-foot Mané flopped, and the former Betis man fell on the ball and struck it with his hand outside the box, meaning he was sent-off by the referee. But many at West Ham disagree with the decision and claim that Adrián was fouled by Mané before he handled the ball outside the box.
Jussi Jaaskelainen, 39, a Finnish goalkeeper, replaced Adrián and pulled off a few good saves, when West Ham, after Andy Carroll's injury, were effectively playing with only nine men. Carroll, 26, was injured and was effectively limping throughout the closing stages of the match. He has a long standing knee problem but he bravely stayed on to help his 10-men side. He left the pitch on crutches.
The Hammers were organised throughout and were determined to hold out for their first clean sheet in 18 away games. They managed to cling on for what could prove to be a vital point in their race for the European places, as they sit in eighth, only eight points off the Champions league places. The Hammers next match is away to Tottenham.
Ronald Koeman's side dropped to fourth, one point ahead of fifth-placed Arsenal, and a point behind Manchester United. They have only been outside the top-four for two weeks since September. This latest result could feel like a missed opportunity to win three points at home and secure third place. Southampton's next match will be also at home to Liverpool.