Virgil van Dijk said Liverpool must be "absolutely spot on" if they are to stand any chance of progressing from their Champions League quarter-final with Paris Saint-Germain.
Van Dijk's comments came after Liverpool were beaten 2-0 by the defending champions at the Parc des Princes on Wednesday, in an incredibly one-sided first leg.
PSG led in the 11th minute through Desire Doue's deflected effort, and they squandered several chances through Khvicha Kvaratskhelia and Ousmane Dembele in the first half.
Kvaratskhelia sealed the win just after the hour when he rounded Giorgi Mamardashvili to score, having been picked out by Joao Neves' sensational pass in behind.
PSG were also denied a penalty for Ibrahima Konate's challenge on Doue, though Luis Enrique's side will still take a comfortable lead to Anfield next Tuesday.
Liverpool have now lost four consecutive away games in all competitions for the first time since doing so between February and April 2012, and they were well beaten here, having registered an expected goals (xG) total of just 0.18 from three shots, compared to PSG's 2.2 from 18 attempts.
It was also the first time since facing Atalanta in November 2020 that the Reds failed to have a shot on target in a Champions League match, and Van Dijk acknowledged they were distinctly second best as he urged them to improve next week.
"Tough, tough work. Always expected. I think we defended with a lot of bodies around the box," Van Dijk told TNT Sports. "Unfortunately, the first goal is a deflection.
"We get some small moments on the break where we could have done better. But now it's a quick turnaround, and we have Fulham waiting for us as well."
When asked about what Liverpool needed to do in the second leg, van Dijk added: "We have to be absolutely spot on.
"Hopefully, our fans can play a big part in that. Our fans are the backbone of the club, and hopefully they can be there for us."
Liverpool started the game with a change of formation, playing five at the back as Van Dijk joined Konate, Joe Gomez, Milos Kerkez and Jeremie Frimpong in the backline.
"They always move around everywhere," Van Dijk said on Liverpool's decision to play with five defenders.
"We have to communicate and follow your man and take risks in that sense. As well as waiting for the right moment to win the ball.
"Hopefully, we can be much better, especially in possession, at Anfield."
Liverpool have lost three consecutive matches in all competitions for the third time this season.
It is the first time they have had three runs of three consecutive defeats in a campaign since 1953-54, when they were relegated from the top flight, piling more pressure on Slot.
And the Dutchman echoed the thoughts of Van Dijk, suggesting that a two-goal deficit somewhat flattered his side heading into the second leg.
"If you reflect on the whole game, I think we were lucky with only losing 2-0," Slot said. "The first goal felt harsh.
"I think it is very good for us that we are still in the tie, we can bring them to Anfield, and we know how good Anfield can be for us."