The influential Reds defender was forced off in the 11th minute of Saturday's 2-2 draw with Everton after a horror challenge from Jordan Pickford.
His absence was felt as Liverpool conceded two headed goals to Michael Keane and Dominic Calvert-Lewin at Goodison Park.
Reports have since claimed Van Dijk has suffered cruciate ligament damage and could be sidelined for up to eight months.
The news has seen Liverpool's title odds fall to 15/8, while Man City have climbed to 5/6 after their 1-0 win over Arsenal.
Alex Apati of Ladbrokes said: "Liverpool are yet to set the world alight this season, and Virgil van Dijk's injury has had a massive impact on their odds of lifting the title for a second successive year."
Somehow, Pickford escaped a red card and VAR review after recklessly crashing into Van Dijk in the box.
Liverpool boss Jurgen Klopp admitted his star man's injury did not look good.
Premier League title outright odds
Man City - 5/6
Liverpool - 15/8
Tottenham - 12/1
Chelsea - 16/1
Everton - 16/1
Arsenal - 25/1
Man United - 33/1
Leicester - 50/1
He said: "It is not good. Virgil played I don't know how many games in a row, he plays with pain, but he couldn't play on and that's not good.
"When I leave the pitch Thiago tells me in the Richarlison red card situation he thinks he got injured.
"It was a clear penalty I saw and then we saw the flag went up. I thought they would still look at the foul but that didn't happen.
"I don't want to say Jordan Pickford wanted to do it but it is not a challenge how a goalie can do in the box."
Man City are now odds-on to win the 2020/21 Premier League title after a serious-looking knee injury to Liverpool's Virgil van Dijk.