Graeme Souness says he's worried about Liverpool as they're too reliant on their misfiring front three "getting their sparkle back".
The Reds have been cruising in the Premier League for the past few seasons, but have hit something of a road block in recent weeks.
Liverpool went three games without scoring following their goalless draw with rivals Manchester United on the weekend - their longest period without netting since 2005.
Souness usually has nothing but good things to say about his former club and Jurgen Klopp's handling of the Anfield giants.
But the Scot is worried for the first time in a long while that when striker Sergio Aguero returns for Manchester City he'll turn them back into serious title contenders.
And unless Liverpool start firing again, they may quickly lose their crown.
"I worry for Liverpool in terms of - there's no [Virgil] van Dijk coming this year. [Joe] Gomez will come back. So nothing changes in personal for them," Souness said on Sky Sports.
"Thiago [Alcantara] will get fitter and be more of an influence.
"They are relying on that front three getting that sparkle back, they're 18 points worse off than where they were at this time last year - that's a hell of a lot of points.
"I worry as a Liverpool supporter than Aguero gets fit and plays 10 games. You only have to look at the game in mid-week against Brighton, [City] huffed and puffed against Brighton but they ended up winning 1-0.
"If Aguero plays in that game I think Aguero gets a couple of goals.
"You can't rely on your centre-half getting a couple of goals, as they did today; freekick from Raheem [Sterling], and then a wonder goal from [Ilkay] Gundogan.
"City are for me the biggest danger for Liverpool and I know there's a couple of ifs in there but if you push me I'm going to go for City [being Liverpool's biggest title threat] tonight.
"I think we will see Aguero agan."
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