Crystal Palace have launched their bid to sign £10million-rated Patrick Van Aanholt from Sunderland.
Palace have made an initial offer of around £6million plus around £2m add-ons which will be rejected but Sam Allardyce is hopeful he can reach agreement with his former club.
Sunderland though will not allow Van Aanholt to leave until they have found a replacement.
Manager David Moyes is willing to sacrifice the 26-year-old Dutchman for much-needed funds to strengthen elsewhere.
Moyes has resisted West Ham's offers for Jermain Defoe because his goals are priceless to the team's cause and while Van Aanholt has had a good season, a more defensive left-back may be required for the relegation fight ahead.