That’s according to Sky Sports pundit Paul Merson, who says Maurizio Sarri’s side would be mid-table without the key duo.
Chelsea have experienced a summer of change buoyed by the high-profile arrivals of Jorginho, Kepa Arrizabalaga and Mateo Kovacic at Stamford Bridge.
But they face the prospect of potentially seeing Hazard and Kante following in the footsteps of Thibaut Courtois, who left them for Real in a £35m deal.
Real have until the end of August to complete their remaining business and the Chelsea duo are of the required calibre to star at the Bernabeu.
Merson claims Chelsea might field offers for Hazard and Kante if Real wave goodbye to Luka Modric, who’s being chased by Inter Milan.
“I don’t know what’s going to happen at Chelsea, if I’m honest,” Merson told Sky Sports.
“You have to remember, the Spanish window hasn’t finished yet.
“If Luka Modric does go and Real Madrid have all that money to play with, they go for Eden Hazard and N’Golo Kante and then suddenly, Chelsea are a mid-table team.”
Merson has also raised doubt about Chelsea’s decision to make Kepa the world’s most expensive goalkeeper.
“I like Jorginho, he’s top drawer,” Merson added.
“Mateo Kovacic from Real Madrid could be anything, but the goalkeeper is only 23 – you tell me how many world class goalies there are at 23, if any.
“In time, it could be a good transfer, but not now.
“This is going to be hard for Kepa, he will probably turn out to be great, but that is a lot of money for a kid and in goalkeeping terms, he is a kid.
“It’s very rare you get goalies that young going for that much.
“It’s a lot of money.”
Meanwhile, Chelsea missed out on a deadline day deal for Nabil Fekir with Lyon chief Jean-Michel Aulas said to have bumped up his price tag to a mega £72m.
Chelsea transfer news: What business did the Blues do this summer?
Jorginho (Napoli) £57m
Robert Green Free
Mateo Kovacic (Real Madrid) Loan
Kepa Arrizabalaga (Athletic Bilbao) £72m
Mitchell Beeney (released)
Wallace Oliveira (released)
Trevoh Chalobah (Ipswich) Loan
Nathan Baxter (Yeovil) Loan
Reece James (Wigan) Loan
Dujon Sterling (Coventry) Loan
Lewis Baker (Leeds) Loan
Jake Clarke-Salter (Vitesse) Loan
Danilo Pantic (Partizan) Loan
Jonathan Panzo (Monaco) Undisclosed
Eduardo (Vitesse) Loan
Kenedy (Newcastle) Loan
Jhoao Rodriguez (Tenerife) Loan
Jamal Blackman (Leeds) Loan
Todd Kane (Hull) Loan
Mason Mount (Derby) Loan
Jeremie Boga (Sassuolo) Undisclosed
Mario Pasalic (Atalanta) Loan
Nathan (Atletico Mineiro) Loan
Jacob Maddox (Cheltenham Town) Loan
Victorien Angban (Metz) Loan
Kasey Palmer (Blackburn) Loan
Kyle Scott (Telstar) Loan
Thibaut Courtois (Real Madrid) £35m