Slutsky was forced into a change of his initial squad when an ankle injury forced Alan Dzagoev out of the tournament, but any concerns over Neustadter's status were quelled when his documents were processed this week.
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Slutsky said on Tuesday: "I think it's not a secret that Roman can play a central defender or a midfielder.
"I didn't plan to invent any new position for him. We have two weeks to decide at which of the mentioned positions he will be more useful for the team."