Besiktas boss Ole Gunnar Solskjaer is reported to be interested in bringing Casemiro to the the Turkish Super Lig, with the Red Devils needing to raise funds.
Current United boss Ruben Amorim has only been in charge since November last year, but the Portuguese head coach has faced significant scrutiny for his side's performances this term.
United finished 15th in the Premier League with just 42 points, and their failure to win the Europa League final against Tottenham Hotspur means they have missed out on Champions League qualification.
The club are said to be under severe financial pressure, and Amorim faces the prospect of having to sell members of his squad in order to fund a rebuild.
According to Turkish outlet Fanatik, Casemiro has been identified as a target by Besiktas, and could look to take advantage of the fact that the Brazilian has just a year remaining on his deal.
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Can United raise enough funds from midfield?
With the team experiencing financial difficulties off the pitch, there is concern that they may be forced into selling attacking midfielder Bruno Fernandes, who is attracting interest from the Saudi Pro League.
His reported price tag of £100m would make a sale tempting, and he may be the most sellable asset in midfield, especially considering Casemiro is 33.
While Kobbie Mainoo could bring in a good transfer fee, the 20-year-old has suffered from injury issues this term and potential suitors may be wary of spending significant sums on him unless he can prove he can overcome his fitness concerns.
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Is Casemiro symbolic of United's decline?
United have been accused of spending recklessly in the past seasons in order to achieve immediate success while ignoring the long-term future of the club.
When Casemiro was bought from Real Madrid in the summer of 2022 for £60m plus £10m in add-ons, he was signed to a four-year deal despite already being 30 years old.
If United are to move forward and free themselves of financial difficulties, they must learn from the mistakes made in the past and look to sign players with potential for growth.