Southampton overcame the second-half dismissal of Victor Wanyama to beat West Ham 1-0 at St Mary's and maintain their excellent recent Premier League form.
Maya Yoshida scored the only goal of a tightly-contested game in the ninth minute on Saturday evening, finishing from Wanyama's pass.
Saints midfielder Wanyama was then shown a straight red card early in the second half after diving in recklessly on Dimitri Payet.
But the hosts withstood a late spell of pressure to record their fifth successive clean sheet and fourth win in their last five matches.
Saints boss Ronald Koeman, who was named Premier League Manager of the Month for January, made three changes from the goalless draw at Arsenal in midweek, with Graziano Pelle starting his first game since December and Yoshida and Jordy Clasie also coming into the starting XI.
Charlie Austin and Andy Carroll started on the respective benches while Cheikhou Kouyate missed out for the Hammers, who made a slow start to the match and soon fell behind.
Adrian was forced into an early save to keep out Cedric Soares' close-range header before Wanyama was allowed to run into the box unchallenged and cut across for Yoshida to finish from close range after nine minutes.
Pelle then headed over the bar as Saints looked to press home their advantage.
The Hammers improved as the half wore on without creating any clear-cut chances against a solid Saints defence.
Fraser Forster, who is yet to concede since returning to the side on January 13, was called into action to keep out a header from Winston Reid while Enner Valencia had appeals for a penalty waved away after a challenge from Yoshida.
The hosts were reduced to 10 men early in the second half when Wanyama dived in on Payet in the centre-circle and referee Mark Clattenburg decided on red, after initially appearing to go for a yellow card.
But the Hammers still struggled to create any clear chances and instead it was Shane Long who wasted a good opportunity when he missed the target after James Collins' miscued header.
Austin also spurned a late opportunity on his home debut when he sliced wide, while new West Ham signing Emmanuel Emenike headed past the post from Sam Byram's cross.
West Ham piled on the pressure in the closing stages, launching balls into the box towards Carroll, but Saints held out to take all three points.
Player ratings
Southampton: Forster (7), Cedric Soares (6), Van Dijk (8), Fonte (8), Yoshida (7), Bertrand (6), Clasie (7), Wanyama (4), Mane (5), Long (6), Pelle (6).
Subs: Romeu (6), Ward-Prowse (5), Austin (5).
West Ham: Adrian (6), Tomkins (6), Reid (5), Collins (6), Cresswell (6), Song (5), Moses (5), Noble (6), Payet (5), Antonio (5), Valencia (5).
Subs: Carroll (5), Byram (5), Emenike (5).
Man of the match: Virgil van Dijk.