Everton have confirmed midfielder James McCarthy suffered a double leg fracture against West Brom on Saturday afternoon.
Toffees boss Sam Allardyce described the leg break as an "awful injury".
Allardyce was speaking after the Toffees confirmed the midfielder had broken his tibia and fibula after Salomon Rondon's follow through from a shot connected with his right leg.
Medics rushed onto the field to treat McCarthy, with Rondon in tears having seen the after-effects close up.
Allardyce added: "We'll do the operation as quick as we can. He's paid a heavy price for his commitment there. A big blow for him and us. This will keep him out until next season at some stage."