Norwich City Head Coach Daniel Farke has revealed winger Onel Hernández is facing "at least three months" on the sidelines after he slipped climbing some stairs to his flat.
Hernández, who became the first Cuban to play in the Premier League last weekend, sustained the injury on Thursday at his home.
He will have a scan on Friday to assess the full extent of the damage, but Farke confirmed he has definitely suffered a lateral meniscus tear.
There are even fears that he may have ruptured his ACL, which would effectively rule him out for the season.
The club have already booked him in for surgery on Monday, and Farke admitted that he will be a huge loss.
"It sounds a bit funny, but the result is, If I'm honest, pretty horrible for us," Farke said.
"Onel slipped on the way to his flat, he slipped on the stairs and fell on his knee. It's definitely a lateral meniscus tear, so we have to wait for the scan, but 95% it's confirmed.
"We also have to check if there's something wrong with his ACL. We need his pace in the offensive side of the game. If he is out for that long, several months, it's a big blow for us."
Farke also confirmed he will be without a number of other key players for the visit of Newcastle United on Saturday, with centre-backs Christoph Zimmermann and Timm Klose still not fit.
Added to that, striker Josip Drmić will also sit out the clash with a hamstring strain and midfielder Kenny McLean is a "major doubt" with a back injury.
Young striker Adam Idah will probably have to watch from the stands too after he injured his back.
Norwich City v Newcastle United, Premier League, Saturday 17 August, 3pm