Newcastle defender Sven Botman is set to have knee surgery and will be out of action for up to nine months.
A scan revealed the centre-back, 24, suffered an anterior cruciate ligament (ACL) injury in Newcastle's 2-0 defeat at Manchester City on Saturday after limping off in the 83rd minute.
The Dutch international has made 17 appearances in the Premier League this season having sustained a knee injury last September which ruled him out for nearly three months after he "elected for a non-surgical rehabilitation plan".
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Botman said: "It is difficult to accept that surgery is out of the question, after fighting so hard to avoid this step.
"The support and love I have already means a lot to me.
"I won't be able to do what I love the most for a while, but after my knee problems recently, I know I will come out of this period a better player.
"My team Newcastle United remain the most important and I will continue to support you every day."
Botman's injury is another blow to manager Eddie Howe and their European qualification hopes - they currently sit four points behind seventh-placed West Ham.
He has struggled to regain the form of his first season on Tyneside, during which he played a key role in the club's top-four finish.
The 24-year-old told Sky Sports in January that he had played on with his previous knee injury without its full severity being known.
Botman chose not to have surgery after the first injury in September as he wanted to get back and help the team in the midst of their injury crisis.
The club were in favour of him having surgery on his ACL but there was no definitive answer having sought the opinion of multiple specialists.
Botman is the latest member of the Newcastle squad to face a lengthy lay-off during the campaign, with goalkeeper Nick Pope still working his way back from a shoulder injury and midfielder Joelinton and striker Callum Wilson also sidelined for extended periods.
In addition, Emil Krafth, Matt Targett, Elliot Anderson, Jacob Murphy, Joe Willock and Harvey Barnes have all endured significant spells in the treatment room, while summer signing Sandro Tonali is serving a 10-month ban for breaching betting regulations.
Why was Botman allowed to play on?
Sky Sports News reporter Keith Downie:
"It's a question many have been asking. I remember interviewing Botman back in January and he said he'd decided to rest up and try and allow the knee to recover rather than face surgery because he felt he would have got himself back into the team and help his team-mates. Back in October, November, Newcastle were in the middle of an injury crisis and were involved in the Champions League and cup matches, as well as the Premier League.
"It's so rare you see a footballer suffer an ACL injury like that and not face surgery, but that was something that Botman and the club as well decided to do.
"My understanding is that the club were happy for him to have surgery at the tail-end of last year, but that Botman - because he wanted to help his team-mates - decided not to have it so he could get back sooner. The club and Botman took on a lot of advice from specialists; there was no definitive answer as to the best course of action, and I think Botman started to feel better towards the end of the year. But since he has returned, he hasn't looked the same player as before the injury when he was a colossus. The news now is not a surprise because he hadn't looked the same.
"It's a huge amount of time for a player of his value and calibre to be out. Newcastle have been beset by injuries this season. We've seen Isak, Barnes and Willock all suffer injuries - and then suffer a similar injury again. That's why supporters are asking questions, but I think it's key to say that it was his decision to play on."
Newcastle's remaining fixtures
Saturday March 30: West Ham (H) - Premier League, kick-off 12.30pm
Tuesday April 2: Everton (H) - Premier League, kick-off 7.30pm
Saturday April 6: Fulham (a) - Premier League, kick-off 3pm
Saturday April 13: Tottenham (H) - Premier League, kick-off 12.30pm
Saturday April 27: Sheffield United (H) - Premier League, kick-off 3pm
Saturday May 4: Burnley (a) - Premier League, kick-off 3pm
Saturday May 11: Brighton (H) - Premier League, kick-off 3pm
Sunday May 19: Brentford (a) - Premier League, kick-off 4pm
To be arranged: Man Utd (a) - Premier League