If doctors are not convinced by the latest knock - one that has ruled him out of qualifying games in Cyprus on Saturday and San Marino next Wednesday - Wales could ask for Koumas to be omitted from Wigan's next game.
Toshack said: "It was important that our medical people had a look at him to find out what the problem was. I knew he had a problem after Wigan's game against Manchester United and I immediately phoned their manager Chris Hutchings. We made sure we had a look at it. Obviously, we are entitled to do that. We have discovered that it's his hip. He's in some discomfort. It's been concerning him for four or five weeks.
"Jason wasn't in the Czech Republic, Dublin, Slovakia and now he's missing the next two. There's nothing we can do. Is it one of 'those things'? No, it's four or five of 'those things'. It's a shame because there's no doubt he gives us quality."