"Of course it is very disappointing, first for the player and also for the team because he's a key player and always in the starting lineup," the Dutchman told reporters ahead of his side's visit to 16th-placed Swansea City.
Koeman, hailed as one of the best defenders in the world during his career, said he had given Wanyama some pointers to help him improve his decision-making.
"I've spoken to him and said sometimes it's better to stay on your feet," he added.
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"He's suspended for five games and that's a long time but we have to accept that. We have enough competition in the squad to replace Victor."
Midfielder Steven Davis has shrugged off the knock he picked up against West Bromwich Albion in mid-January and is fit for the trip to Swansea, while defender Matt Targett is back after missing the West Ham game.
Southampton are seventh in the table and will register their sixth Premier League clean sheet in a row if they stop Swansea from scoring on Saturday.
(Reporting by Simon Jennings in Bengaluru; editing by Toby Davis)
