And Moyes says he will target a replacement when the window opens next month.
"Kurt has been very good for us. Everybody has been impressed. He has the experience from Chelsea and he's a big miss," said Moyes.
"But other players helped us get into Europe last year. They are ready to play. Hopefully they will be good.
"We have been looking to add to the forward players. We tried in the summer for a forward but there was nothing. Now we have to consider looking for a defender if possible.
"I'll see what we think the recovery time of players coming back is as well, that could have an influence on whether we need to take somebody immediately or if we think we can wait a bit later in January."
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