Jamie Carragher has urged Liverpool to "go big" in the January transfer window and sign a new defender following Virgil van Dijk's injury blow.
Van Dijk is facing a lengthy spell on the sidelines after suffering a serious knee injury during the 2-2 draw with Everton on Saturday.
The Dutch centre-back was instrumental in Liverpool 's Premier League title win last season - and Carragher believes his old club must now change their transfer plans as a result.
"Liverpool's next big signing had to be centre-back anyway, and I'm talking about next summer," Carragher told Monday Night Football on Sky Sports.
"(Dejan) Lovren went, they didn't replace him in the squad. They've only got three centre-backs - one of them, (Joel) Matip, is always injured - and there were question marks getting spoken about (Joe) Gomez.
"So there's no doubt Liverpool had to go big in the transfer market next summer. That was the next one.
"That's got to be brought forward to January the first. Not the end of January, not negotiating with a club - whoever your target was next summer."
Carragher named 21-year-old France international Dayot Upamecano of RB Leipzig as a possible Liverpool signing.
"There's a young guy everybody is talking about, Upamecano, who's at Leipzig," he added. "There's talk of him.
"He's not the profile of van Dijk, I think he's only 6ft 1in or 6ft 2in, but if that's who Liverpool wanted next summer, bring it forward, pay extra money and do it on January the first.
"That means Liverpool would have to get through the next 11 league games without Virgil van Dijk.
"I think they have to go big in terms of a signing."
Meanwhile, Carragher highlighted one of the areas Liverpool will need to improve in the absence of van Dijk.
“The huge difference with Virgil van Dijk in what he’s changed at Liverpool is set pieces and balls into the box," he said.
“That’s exactly what we saw at the weekend - look at the (Michael) Keane goal.
“What I want to say on this is he’s not there, so almost forget him - he’s not going to be there in midweek against Ajax or next week in the Premier League.
“The Liverpool players all have to raise their game by five or 10 per cent in these situations.
“It doesn’t mean they can’t defend without him but look at the Everton players around the goalkeeper.
“Right away, if I’m in that position, van Dijk has gone off, I need to be ready, but the Everton players were on their toes, ready for the ball coming in when Liverpool’s players hadn’t moved.
“Keane gets his head on it but if he didn’t, Mina would. Those situations are what I’m talking about.”
Carragher continued: “You go from the first year of Klopp to last season, they’ve conceded 60 per cent fewer goals from set pieces.
“In a low-scoring game, which football is, that’s huge.
“Van Dijk is the best in the air and I’ve mentioned Liverpool players having to do more.
“The second goal comes from a cross - when I say do more, Liverpool aren’t going to be better at dealing with crosses, they’re going to be worse, so stop crosses.”
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