Leeds utility man Stuart Dallas has been ruled out indefinitely after fracturing his thighbone in the defeat to Manchester City on Saturday.
Dallas was left in clear distress following a challenge on Jack Grealish in stoppage time at the end of the first half at Elland Road with the score at 1-0 to the visitors.
The 31-year-old was swiftly stretchered off as the Leeds medical team recognised the significance of the injury.
The club have since confirmed Dallas spent the night in hospital having suffered a femoral fracture. The Northern Irishman is now set to undergo surgery and further tests.
According to Phil Hay, Dallas has sustained 'significant damage' to his knee cap.
A Leeds statement read: "Stuart Dallas faces a lengthy period out of action due to a femoral fracture sustained in yesterday’s Premier League game with Manchester City.
"Stuart was kept overnight at Leeds General Infirmary and will now travel to London for surgery and further tests.
"It is impossible to put into words just how important Stuart is to Leeds United on and off the field.
"Anyone who knows Stuart, knows he will come back from this stronger than ever, and in the meantime, he is sure to make his presence known at both Thorp Arch and Elland Road.
"There’s only one Stuart Dallas."
Leeds were eventually soundly beaten by City, with three more goals flying in after Dallas was stretchered off.
Speaking after the match, head coach Jesse Marsch said: "We don't think it's good with his knee and obviously, with where we are in the season, we will miss him very much because he is in many ways the heart and soul of the group and one of the guys that I think is always at the forefront in terms of being a leader and someone who, who can stand up to big challenges.
"Our hearts and minds are with him and his family and we're hopeful that the prognosis is okay, and that he can have a speedy recovery and get himself healthy and back on the pitch again soon."