The Ukrainian international joins his fellow full-back Nathan Patterson on the sidelines and won't be seen in an Everton shirt again until at least the beginning of next season.
Patterson was ruled out a few weeks ago and now both he and the player who joined the Blues with him in January 2022, are in a race to be fit for this summer's Euros.
For Mykolenko this has been a season in which he has consistently played and been generally a solid performer and a player who has somewhat gone under the radar in this tulmultuous campaign.
In a sense he has been the first-choice at left-back almost by default with no one else an obvious alternative to replace him.
And although Mykolenko has had a decent season defensively there is still questions marks over whether he is dynamic and attack-minded enough for a modern full-back in the Premier League.
Fortunately, there are only three matches of the season left and Everton are already safe and secure with in theory nothing left to play for other than pride and going for the highest possible finish in the League.
So, I suppose it is not too bad a time for Sean Dyche to lose both his young full-backs and he does have replacements who can fill the positions at least until the campaign concludes.
Ben Godfrey and Ashley Young are those players and so presumably those two together with Seamus Coleman if he is fit enough, will be playing there in the last three games.
Longer-term though there are still for me questions about whether either Patterson or Mykolenko are the solution if the Toffees are to really improve.
I think the main areas within the squad that Dyche needs to look at are obviously strikers and wide attackers, central midfield and full-back.
Patterson's injury problems are a major issue while the questions over Mykolenko's attacking contribution are still to be resolved.
For the manager to deal with all this will certainly be a big task and he needs stability behind the scenes and some money to spend.
The crucial question is of course, will he get it?