Alisson suffered another nightmare as Liverpool's title defence was left hanging by a thread after a late collapse at Leicester.
The goalkeeper gifted Jamie Vardy a game-changing goal as the Foxes scored three times inside a dramatic final 14 minutes to clinch a 3-1 win.
Alisson, fresh from two huge gaffes against Manchester City, aided Liverpool's late capitulation when he came and missed Youri Tielemans' long pass and Vardy ran the ball in.
James Maddison had already levelled before Harvey Barnes struck to compound the visitors' misery.
Mo Salah had given them a second-half lead but Jurgen Klopp's side are 10 points behind leaders Manchester City – having played two games more – after a third straight defeat.
Vardy also missed two excellent chances when he headed at Alisson and hit the bar in the first half.
It was a stunning turnaround and the Foxes moved into second, six points ahead of Liverpool.
Klopp would have never envisaged such a collapse after a bright start, despite Maddison trying to lob Alisson from inside his own half.
Jordan Henderson's raking 50-yard pass sent Salah clear of Ricardo Pereira yet the forward failed to get the ball under control as he burst into the area.
Vardy lifted the ball over from an angle after Barnes picked him out and Liverpool's injury worries continued when James Milner was forced off after just 17 minutes, Thiago replacing him.
It failed to dent the visitors' momentum, though, and they continued to probe with Salah giving Pereira a difficult half.
The Egypt international skipped away and his cross was turned wide by Sadio Mane before Kasper Schmeichel produced a world-class save to deny Roberto Firmino's header – although Henderson was flagged offside in the build up.
Leicester's sloppiness with the ball aided their top-four rivals but they should have opened the scoring nine minutes before the break.
Barnes picked out Vardy in the area but, unmarked seven yards out, he headed straight at Alisson.
It was a chance the former England striker would usually take and he missed another golden one soon after.
Debutant Ozan Kabak's slip allowed Maddison's impudent flick to send the striker clear but his rising drive hit the bar.
For all their possession, Liverpool could have gone into the break two goals down but started the second half as they did the first, pinning the Foxes back.
Klopp's side struggled to create clear openings but did come close after 57 minutes.
Pereira brought down Salah and Trent Alexander-Arnold's 30-yard free kick clipped Vardy in the wall and bounced off the bar.
Leicester's resolve looked like holding firm, with the returning Wilfred Ndidi quietly efficient, but Liverpool finally broke through after 67 minutes.
Alexander-Arnold found Firmino in the area and his cute turn teed up Salah to curl into the corner from 15 yards.
Liverpool looked on course for victory but collapsed in a frantic final 14 minutes.
First Leicester thought they had a penalty after Thiago brought down Barnes, only for VAR to rule the foul came outside the box.
It mattered little though as Maddison's low free kick flashed straight in – although it was only given after a VAR check with Daniel Amartey ruled fractionally onside.
Three minutes later Alisson rushed out to Tielemans' pass but clattered into Kabak instead to leave Vardy with a simple finish.
It got worse for the visitors with five minutes left when Barnes broke free on the left and fired past Alisson.
