Monk has warned Marvin Emnes he must improve his fitness if the Middlesbrough forward moves to the Liberty Stadium on a permanent deal.
He told the South Wales Evening Post: "I've talked to Marvin about how I feel going forward.
"I like him, but he needs to improve on a lot of things - his fitness for one.
"It is a case of the club speaking to his representative and seeing what happens.
"There's no definites here and there just yet but we will see in the coming weeks."
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