Jamie Carragher believes Liverpool will "lift the hopes" of their Premier League title rivals if they fail to sign a centre-back in January.
The Reds have been grappling with a defensive injury crisis for much of the campaign with Virgil van Dijk and then Joe Gomez sidelined by long-term serious knee problems.
Joel Matip has been restricted to just nine starts and is out for at least the next fortnight with an adductor complaint.
Fabinho has been pressed into an emergency centre-back role with 19-year-old Rhys Williams and Nat Phillips - neither of whom had played in the Premier League before this season - competing to partner the Brazilian.
Despite the concerns, Liverpool went into the New Year top of the table with just one defeat from their first 16 league matches.
But Reds legend Carragher is convinced Jurgen Klopp's side would be offering unnecessary encouragement to their fellow championship challengers if they don't bolster their centre-back options during this month's transfer window.
"The injury to Virgil Van Dijk alone will cost Liverpool between nine and 12 points over the course of this season," he said.
"And although Fabinho has proved a fantastic deputy at the back, Joel Matip’s ongoing problems means, to me at least, that it is inconceivable that Liverpool will not sign another centre-half at the earliest opportunity.
"I cannot understand the logic of not doing so. The club needed one anyway."
Carragher, writing in the Telegraph, added: "If Matip continues to be in and out of the side, and then Fabinho gets injured, how can Liverpool expect to perform at the highest level with only the inexperienced Rhys Williams and Nat Phillips to step in? That is too big a risk.
"The way Liverpool have dealt with the loss of key players so far shows they will still take some stopping, but it will not be as one-sided as last year and failing to sign another defender will only lift the hopes of everyone else.
"Jurgen Klopp will be cursing a missed opportunity if Liverpool do not retain their title. Liverpool are the best team in England, but circumstances have opened the door for everyone with dreams of catching them."
