Striker Michy Batshuayi is set to sign a contract extension with Chelsea before a loan move to Crystal Palace.
The 26-year-old's current contract runs until next summer, so the new deal will mean the Belgium international does not leave on a free transfer.
Batshuayi went on loan to Palace in the second half of 2018-19, making 13 appearances and scoring six goals.
His move ends the chances of Chelsea midfielder Conor Gallagher joining Palace on loan.
Premier League clubs can only sign one player on loan from a specific club at any one time.
Gallagher, 20, spent last season on loan at Swansea City.
Batshuayi's playing opportunities at Chelsea have been limited, and are set to narrow further after the Blues spent about £47.5m on forward Timo Werner and £71m on attacking midfielder Kai Havertz.
Last season he only made one Premier League start, at home to Manchester United.
Meanwhile, Chelsea are closing in a deal for Rennes goalkeeper Edouard Mendy.
The Premier League club has already had a bid for the 28-year-old Senegal international rejected.
But manager Frank Lampard wants to increase competition with first-choice keeper Kepa Arrizabalaga.
Their record £71m signing made a number of errors last season and was dropped in favour of second-choice keeper Willy Caballero, who turns 39 later this month.
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