The Dutchman is regarded as the Premier League's best defender and Barnes thinks his absence is why the Reds lie fourth in the table.
He told talkSPORT: "When you're so used to playing a particular style with a particular way with three hard-working midfield players, you've got van Dijk at the back who gives you that assurance, which allows the full-backs to go forward with conviction and be creative.
"All of a sudden, the psychological effects of Van Dijk not being there affects the whole team.
"So it doesn't necessarily physically affect the team in terms of what they do, but if you look at Trent Alexander-Arnold, for example, or even Andy Robertson, when Van Dijk is there they know they can go forward with conviction knowing that they're safe at the back.
"I don't think they're being as creative."
Barnes also admitted he sees no goal threat in midfielder Thiago Alcantara.
The 29-year-old arrived from Bayern Munich last summer and made his Anfield debut during Sunday's 0-0 draw with Manchester United.
Despite impressing with his array of passing, former England international Barnes doesn't think he helps the front three of Mohamed Salah, Roberto Firmino and Sadio Mane.
"Thiago, who was running the game and was the best player in the first-half, I don't think that necessarily helped the front three," the 57-year-old continued.
"With Henderson and Fabinho in midfield, they just get the ball forward and are much more direct for the three strong-running strikers to get on the ball and go on attack, Thiago slows the game down.
"When he slowed the game down in tight areas, that is not Mane's game, that is not Salah's game. So we're getting used to a new system, but at the moment it's not working."
Liverpool have gone three games without a goal in the league and that's their longest run since 2005.
They'll be looking to get back to winning ways on Wednesday evening when they face Burnley.
Do you think Virgil van Dijk's injury has had a 'psychological effect' on Liverpool?
Featured Image Credit: PA Images
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