Borussia Monchengladbach chief Max Eberl says keeping hold of Denis Zakaria is touch and go.
With the likes of Manchester City and Arsenal monitoring developments, the Switzerland international's contract is running down this season.
Eberl said: "We can show him a very good perspective.
"If he wants to play for the championship again, then I can't promise him that here.
"But it is clear that he is of outstanding importance to us."
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