Chelsea are still trying to sign Enzo Fernandez from Benfica before the transfer deadline on Tuesday.
The Blues have been in talks to sign the Argentina midfielder throughout January, but the Portuguese club is insisting on his €120m (£105.4m) release clause.
The Premier League club has offered players on loan and on permanent deals but Benfica have so far refused to bulge.
If Chelsea meet their valuation, the transfer for Fernandez would surpass the £100m Manchester City paid Aston Villa for Jack Grealish 18 months ago, making him the most expensive Premier League signing ever.
The 22-year-old is believed to be keen on the move to Stamford Bridge according to Sky Sports.
Fernandez won the Best Young Player award at the 2022 World Cup.
