I am sure that football is nowhere near squeaky clean, but I've posted before that it all goes back to one article by an author who is based in Russia, who maybe isn't the most legit source. The last update to his wiki page is when he tweeted the pro-Russia conspiracy theory about the "fake" bombing of the Ukrainian maternity hospital.
He's written articles diminishing Russian doping, while making big claims about how much doping there is in other countries. Now he may well have the best contacts at Liverpool, but we have no way of knowing. What we do know is that it benefits Russia's efforts to cheat in sport by having rumours that "everyone is at it" circulating.
Near the start of the video linked to, the vlogger quotes a "Fact Check" of the original article.
"However, there has been no definitive proof that the above is true. Yet at no point has there ever been reports to suggest that the above is incorrect."
So, we can make any old shit up, and so long as no-one comes out and disproves it, then it passes the Fact Check?
Here's a link to the author of the original article, and the original article that appears to have started this rumour:
en.wikipedia.org
Alan Moore discusses the reasons why he believes that Liverpool will not retain their Premier League title this coming season.
backpagefootball.com
I'd have a read of his wiki page and then make up your own mind about how likely this it so be true.