German-born Loris Karius and his family have been the focus of hundreds of threats and hate messages on social media after making several mistakes that resulted in goals for the Real Madrid.
Posts from Liverpool fans included a comment saying, “I’ll murder your girl I’ll murder your girl”.
Others said his “sons deserve to die of cancer” and “I hope your whole family dies”.
A spokeswoman for Merseyside Police told The Telegraph officers were investigating the vile abuse, and added, “The force takes social media posts of this nature extremely seriously and any offences identified will be investigated.
Merseyside Police would like to remind social media users than any offences including malicious communications and threatening behaviour will be investigated.”
During the game, which was won by Real Madrid 3-1, Karius threw the ball directly towards Real Madrid striker Karim Benzema who promptly scored.
He also fumbled a shot from the Real Madrid winger Gareth Bale, which resulted in another goal for the Spanish team.
After the game Karius apologised for his two mistakes.
“Today I lost my team the game and I feel sorry for everyone – from the team, from the whole club – that the mistakes cost dearly,” he said.
“If I could go back in time I would. I feel sorry for my team. I know I let them down today. These goals cost us the title basically.
“It’s very hard right now but that’s the life of a goalkeeper. You have to get your head up again.”
When asked how his team had responded to his performance he said, “Of course everyone tried to cheer me up.