Jurgen Klopp said Liverpool only had themselves to blame after West Brom snatched a shock 1-1 draw at Anfield in the latest twist in the Premier League title race on Sunday.
The Baggies remain second bottom of the table, but gave their chances of survival a huge boost by becoming the first side to take points off Liverpool at home this season in Sam Allardyce's second match in charge.
The English champions seemed set for a comfortable afternoon as Sadio Mane's fine finish gave them a deserved 12th minute lead.
Liverpool's dominance of possession reached 84 percent in the first-half as West Brom struggled just to get out of their half.
However, the visitors grew into the game in the second-half and got their reward when Semi Ajayi headed home from a corner.
"It was our own fault," said Klopp. "We gave them simple corners and that's the only thing they wanted to have tonight.
"To be fair West Brom did their job inside 90 minutes. They deserved the point tonight because we didn't finish the game.
"It is not a game we will talk about in 20 years but it is a game we have to play and we didn't play as we could."
Liverpool move three points clear at the top of the table, but a rare slip up at home offers the chasing pack in the title race an unexpected boost.
Just four points separate Everton in second from Southampton in ninth in a tightly bunched table.
Allardyce was the last visiting manager to win a Premier League game at Anfield, when in charge of Crystal Palace back in April 2017.
The former England manager is now unbeaten in his last four away games against Klopp's men with four different clubs and his gameplan again worked to perfection.
"Every man today showed the spirit this team needs to get out of this position," said Allardyce.
"Goals are precious to us and this one has given us a point because we defended so well and we took the opportunity when it came."
- Liverpool 'slack' -
The Baggies set out to limit the sort of damage suffered by Crystal Palace in a 7-0 hammering inflicted by Liverpool last weekend.
Mane ended his longest drought of nine games without a goal as a Liverpool player against Palace and showed his sharpness in front of goal is back with a brilliant touch to control and finish from Joel Matip's pass on 12 minutes.
That could and should have opened the floodgates for Klopp's men given their level of control before the break.
A series of dangerous crosses from Andy Robertson failed to find the finishing touch, while Mane headed just wide from Jordan Henderson's delivery.
"We created a lot of chances in the first half and then in the second half it was as if we didn't want to do it again," said Robertson.
"We went slack. Every one of us made a mistake in the second half which can't happen."
The Reds suffered another injury blow at centre-back as Matip pulled up with a muscle problem and had to be replaced by 19-year-old Rhys Williams.
Despite their lowly position in the table, West Brom have already taken points off Manchester City and Chelsea this season and were extremely unfortunate not to take at least a point away to Manchester United.
Ajayi was denied his first Premier League goal when his strike away to City in a 1-1 draw earlier this month was credited as a Ruben Dias own goal.
But he repeated the trick and this time got the credit with a powerful header in off the inside of the post that this time left Alisson helpless.
Liverpool have made a habit of winning games late in the past two seasons, most recently when Roberto Firmino's injury time header beat Tottenham 2-1 in their last outing at Anfield.
The Brazilian nearly did it again at the death, but his downward header was brilliantly saved by Sam Johnstone.