Swansea are facing a fight to keep hold of Alfie Mawson after West Ham United's interest in the £25m-rated defender grew.
Sky Sports understands that Hammers boss David Moyes is eager to add a new centre-back to his senior ranks in January, and has instructed his board to try and make a move for Mawson.
The 23-year-old has been one of Swansea's better players throughout his 18-month tenure in south Wales, but the Swans would not be prepared to let him go on the cheap even though the chances of retaining Mawson's services appear to be waning.
Mawson is only contracted to Swansea until June 2019 and, if he is unwilling to pen a contract extension at the Liberty Stadium, it could be in Swansea's best interests to cash in on him whilst his value is high.
West Ham already have a number of central defenders available to Moyes, but the Scot isn't exactly keen on those who he can call upon at the present time.
Veteran defenders James Collins has struggled with niggling injuries over the past couple of seasons, Angelo Ogbonna has proven to be inconsistent for the Irons and Jose Fonte was earmarked as something of a disaster signing by co-owner David Sullivan late last year.
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That leaves Moyes with only Winston Reid as a good viable option at centre-back, and the ex-Manchester United and Everton manager will want to strengthen that area of the pitch as a result.
Moyes told reporters of his desire to bolster his first-team squad in the winter window back in December, but admitted it would be difficult to get the numbers in that he wanted.
He said: "I would like to bring in one or two reinforcements, but every manager will tell you it's not an easy time to do business. It's also an expensive month. We'll try and do it but there's no guarantee."
Swansea chairman Huw Jenkins is reluctant to sell Mawson, but if a decent offer comes in for him then it may be difficult to stand in the former Barnsley man's way.