West Ham's £17.5 million summer signing has been ruled out for the season after undergoing surgery for an Achilles injury sustained the 1-0 defeat to bitter rivals Tottenham last time out (whufc.com).
The Ukrainian is the latest in a long line of players West Ham have signed over the years to have suffered a serious long-term injury.
It is a major blow for Manuel Pellegrini.
But the focus now shifts to who the Chilean will use in Yarmolenko's stead.
His options are limited with Michail Antonio, Robert Snodgrass and youngster Grady Diangana the leading candidates.
Pellegrini must forget Antonio, though, and instead reshape his West Ham side to crowbar Arthur Masuaku into the team.
While it may seem outlandish to suggest a defender should replace an attacker of Yarmolenko's quality it is not without logic.
Antonio has had several chances and Robert Snodgrass is earning his starting berth with some full-blooded displays.
West Ham are crying out for pace and service for Marko Arnautovic and Masuaku has it in abundance.
There are however question marks over his defending - and have been ever since he signed for the club - which was evident by his costly mistake against Brighton in a recent 1-0 defeat.
So a rejig from Pellegrini could bring Masuaku's crucial pace back into the team while also freeing up their record signing Felipe Anderson to do damage more centrally.
Playing Masuaku on the left in front of Aaron Cresswell would push Anderson inside into the attacking central role where he can orchestrate attacks and utilise his clever passing skills.
That would then allow Snodgrass to move across to the right to replace Yarmolenko with the likes of Antonio and Diangana as backup.
West Ham travel to Leicester City on Saturday for what is turning into a very important match.