West Ham had goalkeeper Adrian sent off but frustrated Southampton by holding on for a goalless draw at St Mary’s.
The keeper was red carded when he handled outside his box under pressure from Sadio Mane after a clumsy touch.
Mane was denied by a goal-line clearance earlier and Saints pushed for a winner but Maya Yoshida headed over as the Hammers defended bravely.
West Ham’s point came despite an injury to substitute Andy Carroll who was hobbling badly in the closing stages.
The Hammers’ first clean sheet in 18 away games means Southampton dropped to fourth, a point ahead of Arsenal.
Few Saints’ fans could have dreamed their side would be pushing for a top-four finish when players such as Adam Lallana, Luke Shaw and Dejan Lovren left in the summer but this latest result will feel like a missed opportunity.
Ronald Koeman’s side failed to create clear-cut chances before Adrian was dismissed but they dominated the remaining 30 minutes without adding the end product to their approach work.
Striker Graziano Pelle, now without a goal in eight league games, glanced a header wide in added time and in a frantic finish Dusan Tadic was denied by a Jussi Jaaskelainen save.
West Ham played the closing stages with Carroll limping, effectively reducing them to nine capable players but their determined display leaves them eighth, eight points behind their hosts.
Their manager Sam Allardyce this week told reporters “no coach was more sophisticated” than him in the Premier League and he had to make late adjustments to his side, admitting before kick off his staff “haven’t had any real practice with those available” since Sunday’s draw with Manchester United.
Despite being without the injured Kevin Nolan and unwell Mark Noble in midfield, they were still organised throughout.
Aside from Mane’s run and shot which prompted a Carl Jenkinson clearance in the first half, Adrian was relatively untroubled until the hour mark, where the first sending off of his career arrived.
It was a clear dismissal as his decision to try to wrong-foot Mane backfired, prompting panic which ended with the Spaniard falling on the ball and striking it with his hand.
The home side sensed a seventh win in nine league games and introduced January signing Filip Djuricic for his debut but neither he nor fellow substitute Tadic could break the resistance.
Southampton attacked in waves and Aaron Cresswell’s brave block prevented Nathaniel Clyne’s powerful volley, before Yoshida headed over when well placed.
Koeman’s side have now failed to win at home in five of their last seven league games but have only dropped out of the top four for two weeks since September.