That delay looks likely to cost Barkley's boyhood club £20m in transfer revenue although Everton risk losing the England worldwide for nothing in the summer and will reluctantly accept a cut-price move.
Barkley played well for the Merseysiders last season under the management of Dutch boss Koeman.
Tottenham have been monitoring Barkley's situation but Sky Sports suggest the North Londoners have chose to end their interest with Mauricio Pochettino now looking at alternative targets.
Barkley was linked with a move to Stamford Bridge throughout the summer but now finally looks set to join the current Premier League champions.
New manager Sam Allardyce said previous year that if he returned to full fitness and remained committed, he could still have a future at the club.
His news of joining Chelsea for £15 million was first broke by Paul Joyce of the Times, who revealed that Ross Barkley is likely to have a medical today (Friday) at Chelsea with a fee in the region of £15million. He said in his press conference, "I would expect there would be sometime in this window if there is going to be any interest from some of the big boys".
Some of the Everton fans who were disappointed in his decision not to sign a new contract past year will likely be happy to see him leave.