Tony Pulis believes Albion were again wasteful in front of goal after Southampton earned all three points thanks to Sofiane Boufal's individual strike.
Albion were again toothless in attack and only created one clear cut chance when Jay Rodriguez pulled his shot when through on goal.
The defeat sees Albion drop to 13th in the league having not won since mid-August.
"I thought they penned us in for the first half. They're a good side, Southampton," said Pulis.
"They've got some very good players and I didn't think we offered too much of a threat going forward.
"We looked better with two upfront and you'd expect Jay to score his chance.
"I think if we score then we go on to win the game."
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