Everton have confirmed Ben Godfrey has been taken to hospital after the defender suffered a serious lower leg injury.
Godfrey was injured in the 10th minute of Saturday's Premier League match at Goodison Park, as Everton's rotten luck with injuries continued.
The defender's poor backpass resulted in Jordan Pickford attempting to keep the ball in play, and even though the England goalkeeper failed to do so, it was apparently not spotted by the officials.
Play continued and, in an attempt to rectify his mistake, Godfrey lunged in on Kai Havertz, making a clean challenge, but immediately signalled to the touchline and was clearly in some distress as he held his right leg.
After receiving treatment for eight minutes, the 24-year-old was taken off on a stretcher, with Mason Holgate replacing him.
Chelsea took the lead in the stoppage time created by Godfrey's injury, with Jorginho scoring from the penalty spot after Abdoulaye Doucoure's foul on Ben Chilwell.
At half-time, Everton confirmed Godfrey, who required oxygen as he was taken off the field, had been taken to hospital.
Frank Lampard was already without a recognised striker for Everton's season opener, with Dominic Calvert-Lewin set to miss around six weeks with a knee injury sustained in training.