Dejan Lovren admits Liverpool feel "ashamed" after losing their unbeaten record against Watford.
Liverpool suffered their first league defeat of the season on Saturday as Watford beat the runaway Premier League leaders 3-0 at Vicarage Road.
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Jurgen Klopp's side miss the chance to emulate Arsenal's 'Invincibles' by ending the season unbeaten in the league, and Lovren believes the defeat is a "wake-up call" for the Reds as they look to win the Treble.
"It feels like someone has hit us in the face - and we deserved it," said the Croatian, who made his first start in the Premier League since December at Vicarage Road.
"We feel a bit ashamed because there's no excuse for that performance."
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Two goals from Ismaila Sarr and a third from Troy Deeney ended Liverpool's 44-match unbeaten run in the Premier League and Lovren believes the Reds lacked aggression when without the ball.
"It really hurts because from the beginning to the end we were missing all the things we usually have," he added.
"The manager looked at us when he came into the dressing room and I think he knows we are missing something.
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"I think it was about the aggression when we lost the ball and not recovering it as quickly as possible.
"Usually we do it without a problem but against Watford they were always winning the second balls - and that doesn't usually happen with us.
"We need to look at this and realise that we have to do much, much better."
Liverpool remain 22 points clear of nearest rivals Manchester City, who won a third successive Carabao Cup on Sunday after a 2-1 win over Aston Villa.
Klopp's side travel to face Chelsea in the fifth round of the FA Cup on Tuesday before they return to league action at home against Bournemouth on March 7.