Wanyama will be sidelined for the next few weeks, having picked up a third red card of the season during last Saturday’s 1-0 win over West Ham when he tackled Dimitri Payet.
Koeman admitted it was disappointing not to have him available for this run, but explained it is the player himself who is most upset.
"It's very frustrating, but the most frustration is for the player by himself,” Koeman told youtube.com/southamptonfc
. “I think he was a little bit unlucky with that foul.
“The intention was to play the ball, he missed the ball and it was a tough decision the red card, because one day later the tackle of [Mathieu] Flamini in the Bournemouth-Arsenal game was also a red card, and that's the question about a referee to be consistent.
“Victor's unlucky, but he needs to accept it, because it's not one game, it's five in a row. It's a long time and that's difficult for the player.”
Koeman is satisfied with the options he has in Wanyama’s absence, with Oriol Romeu, who came off the bench against West Ham to help ten-man Saints close out the game, having done well in recent weeks.
The Saints boss said: "Oriol is playing well, he's doing well, I think he's improving in what we need as a midfield player in that control position, but we have more competition in the midfield, and we have competition in defence, we have good competition by the attackers and that's what we like to have and then it's always up to the manager to get the best choice in the line-up for this Saturday.