Loris Karius says he should have handled things differently following the disappointment of Liverpool's Champions League final defeat to Real Madrid.
The German goalkeeper made two big errors, which helped Real secure a 3-1 win in the final Kiev.
Liverpool manager Jurgen Klopp signed Alisson a few months after the final and the Brazilian played a major role in the Reds lifting the European Cup for a sixth time in June of 2019.
As for Karius, he moved to Besiktas to try and get his career back on track but it looks unlikely that the Turkish club will sign the 26-year-old on a permanent deal.
"I had a concussion after a blow from Sergio Ramos, which restricted my spatial vision.
"This was unequivocally ascertained in a detailed study by one of the world’s leading brain specialists.
"At first, I was happy to know what was going on in this game. I didn’t want to make it public myself.
"When the result was released, there was a lot of malice and insult, often well below the belt.
"I never used it as an excuse. But when people make fun of someone who has badly injured their head, I have no understanding."
Karius added that whatever he had done previously for Liverpool was no longer remembered and that he will always be associated with the Real Madrid game.
"When I was just 24, I was in the Champions League final. Otherwise only Manuel Neuer and Marc-André ter Stegen were among the active German goalkeepers in the final.
"But my share of it with all my shows and good performances before was suddenly no longer present.
"The reactions were over the top and disrespectful. Above all that it is drawn out in this way. Errors are measured with different, even abnormal, dimensions and are not assessed fairly."
Karius also revealed what it was like to deal with abuse online: "We players face extreme hostility on the internet. If you read every message, you wouldn’t be able to sleep for two days.
"It’s insane what people take out under the guise of anonymity, badly insulting others, discriminating against them and then becoming racist.
"You can’t blame fans if they whistle a player. You pay admission [fee] and have the right to be dissatisfied.
"A professional has to endure that. If there are personal insults or death threats, the line is then crossed.
"There were some of them [death threats]. But I can’t take that seriously. These are people who write anonymously and don’t even show their faces in their profiles."
Karius has been linked with a return to the Bundesliga but with the Turkish season on hold, he said it's hard to know what the next step is.
"I am not involved in speculation. The fact is that I have a contract in Liverpool until 2022.
"At the moment I'm just concentrating on the season at Besiktas. It is far too early to say anything about summer, especially now that nobody knows exactly what to do because of coronavirus."