Matt Miazga is having a medical at Cobham and is expected to put pen to paper on a three and a half deal to join the Blues from MSL side New York Red Bulls.
The 20-year-old, is not expected to be farmed out but will spend the rest of the season acclimatising to the English football scene with Chelsea.
He could also feature in future FA Cup fixtures this season should the Blues get past MK Dons on Sunday.
The move for the centre-back brings into sharp relief the immediate future of English defenders John Terry and Gary Cahill, with Cahill set to be ousted from SW6 as a result of the £3.5million deal to secure Miazga.
Terry is expected to be offered a new one-year deal in the coming months.
Chelsea will listen to offers for Cahill who, under interim boss Guus Hiddink has been frozen out - starting just two matches.
Cahill is worried that a lack of action on the pitch will affect his chances of playing for England in the Euro 2016 in France in the summer.