Isak was injured while putting Liverpool ahead away to Tottenham on Saturday night, having only been on the pitch for twelve minutes after coming on as a second-half substitute.
Isak was tackled hard by Tottenham defender Micky van de Ven, and his left leg was crushed.
No forecast
Sky Sports, among others, has reported that the Swedish star striker is seriously injured. Late on Monday evening, this was confirmed by Isak's club, Liverpool.
The 26-year-old Swede has undergone surgery for an ankle injury and a fractured fibula - and Liverpool has no forecast for how long the blue-and-yellow football star will be out of action.
The news is the worst imaginable for Alexander Isak - but also for the Swedish national team, which in just over three months will play the World Cup playoff against Ukraine in Valencia.
Isak was a huge success at Newcastle last season, scoring goals in the Premier League and helping the club win the League Cup - Newcastle's first title in 70 years.
Heavy autumn
That prompted Liverpool to pay almost 1.7 billion kronor for Alexander Isak ahead of this season. But after a troubled summer, in which Isak refused to train with Newcastle, he has struggled to find form this fall.
The goal against Tottenham was only Isak's second in the Premier League, and his third goal overall in the Liverpool shirt.
Alexander Isak also had a tough autumn in the national team, and his poor form contributed to Sweden's fiasco in the World Cup qualifiers. He was recently awarded the Guldbollen, the award for the best Swedish football player of the year on the men's side.
Liverpool writes that Alexander Isak's rehabilitation is now continuing at the club's training facility.
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