Coleman suffered a double leg break during Ireland's 0-0 draw with Wales last night.
The injury was inflicted by Aston Villa defender Neil Taylor, who received a straight red card for the horror tackle.
Coleman is now expected to face more than six months out on the sidelines.
The top 15 worst leg breaks in football
Fri, March 24, 2017
Express Sport brings together a collection of the most gruesome leg breaks in football – not for the squeamish…
1 of 16
GRAPHIC CONTENT: The top 15 most gruesome leg breaks in football
Ronald Koeman has vowed to support Seamus Coleman
And Everton boss Koeman has offered his support to his star right-back, vowing to help him through the next few months.
"I haven't been able to speak to Seamus as yet and I hope to do so this afternoon, but he will be aware that the thoughts of his team-mates, the coaching staff, everyone at the club and all Evertonians are with him at this time," Koeman told the Toffees' official website.
"No one ever wishes to see something like this happen to any player, much less one of our own.
Get Quotes on Home Insurance
Seamus Coleman will miss the rest of the season through injury
Neil Taylor was dismissed for his tackle on Seamus Coleman
"The medical staff here at Everton are in contact with the medical staff of the Republic of Ireland and we will continue to liaise closely.
"Seamus will face a lengthy recovery period and we will support him throughout this.
"He is a really strong character and he has a great family around him and we, his extended family at Everton, will be here for him to help him get through this over the coming days, weeks and months."