What are the key questions facing Liverpool boss Slot?

Four defeats in a row, fourth in the Premier League table and four points behind leaders Arsenal. Something has gone wrong at Liverpool.

For a team that cantered to the league title last season, Liverpool suddenly look vulnerable at the back, lethargic in midfield and toothless in attack.

To make matters worse, Arne Slot - after spending almost £450m on new talent - doesn't seem to know his best starting XI.

In Sunday's 2-1 defeat by Manchester United at Anfield, summer signings Florian Wirtz, Hugo Ekitike and Jeremie Frimpong - signed for a combined £214.5m - all started on the bench.

"Slot has a dilemma at the moment about how he fits these players in," former Liverpool defender Stephen Warnock said on BBC Radio 5 Live's Monday Night Club.

"It's not always the price tag of a player, or the name of a player, that suits a team. We are seeing that with Thomas Tuchel at England."

BBC Sport has looked at the key questions Slot needs to address if Liverpool are to avoid falling to a fifth consecutive defeat for the first time since 1953.

Mohamed Salah has been Liverpool's talisman for the past eight seasons.

But, after scoring 29 goals in 38 league games last season, the winger has not been firing on all cylinders so far this term.

Salah has not scored in the Premier League since 14 September when he netted a stoppage-time penalty to earn a 1-0 win over Burnley, while he has not scored from open play in the league since the Reds' opening game against Bournemouth.

It is the first time he has gone seven consecutive Premier League games without scoring a non-penalty goal since joining the Reds back in 2017.

The 33-year-old's lack of form was summed up on Sunday when he skewed a golden opportunity wide in front of the Kop as Liverpool were chasing an equaliser.

Salah seems to be lacking confidence when it comes to taking on defenders. Known for his rapid attacking runs, the Egyptian isn't driving fearlessly at defences the way he used to.

Slow build-up play isn't helping Salah, who thrives when attacking at speed and prefers to face defenders head-on, rather than with his back to goal.

Premier League great Wayne Rooney has questioned Salah's recent work ethic and, without contributing in front of goal, more scrutiny has been placed on his reluctance to track back and help out in defence.

But does Slot feel confident enough to drop a player who has been Liverpool's hero on so many occasions?

As a proven Premier League goalscorer and with a British record £125m price tag, expectations were high, and so was the intrigue when Liverpool signed Alexander Isak.

Contrary to most expectations, it has not been an easy ride for the Sweden international since his arrival on Merseyside.

After a drawn-out transfer saga between Newcastle and Liverpool, Isak missed out on pre-season preparation and his lack of match sharpness has been clear. He has come out of his first seven games for Liverpool without a goal to his name.

Fellow summer recruit Ekitike hit the ground running by scoring five in his first eight games.

But opportunities for the Frenchman have dried up since he was sent off for removing his shirt after scoring a late winner against Southampton in the Carabao Cup - a "stupid" second yellow card, according to Slot.

Since then, Slot has favoured Isak in the number nine role and Ekitike has struggled to make an impact from the bench.

But Isak's struggles may leave the Liverpool boss with little choice but to revert back to Ekitike.

Against Manchester United, Isak had just 19 touches in his 71 minutes on the pitch. His replacement Federico Chiesa, in comparison, had 23 touches and provided the assist for Liverpool's leveller.

Should Slot stick or twist with Isak? Or is it possible to squeeze Isak and Ekitike in together?

Wirtz is another big-money summer signing who has not been able to make his mark for Liverpool.

Signed from Bayer Leverkusen in June for a fee that could reach £116m, Wirtz - unlike Isak - enjoyed a full pre-season with the Reds.

But the attacking midfielder has not scored yet in a Liverpool jersey, while his only assist came in their Community Shield defeat by Crystal Palace.

During a season where he scored 10 goals and created 14 more in the German Bundesliga last term, the 22-year-old was usually positioned on the left and allowed to drive inside with the ball at his feet by Leverkusen boss Xabi Alonso.

But this season Slot has employed Wirtz in a more central role behind the strikers.

This change seems to have disrupted the stability of a midfield made up of Ryan Gravenberch, Alexis Mac Allister and Dominik Szoboszlai, who started 22 Premier League games together as Liverpool won the title.

With Wirtz perhaps struggling to adapt to the intensity of off-the-ball demands in the Premier League, Slot has reverted to his established midfield trio, leaving his expensive Germany international on the bench.

Yet Liverpool's attacking sequences have remained slow-moving and lacking in creativity.

Wirtz, in fact, has been creating chances when he has been involved. He has created more chances per 90 minutes than any other player in the division who has played more than 200 minutes.

Should Slot restore his trust in Wirtz and demand that others do better with the chances provided?

Given the attacking threat he posed, losing Trent Alexander-Arnold was always going to affect Liverpool when he moved to Real Madrid.

The right-back scored 23 goals and 92 assists in 354 appearances for the club and Slot has struggled to fill the gap.

It was thought Jeremie Frimpong would be first choice, given his £29.5m arrival in the summer, but the Dutchman has been competing for minutes with Conor Bradley and midfielder Szoboszlai.

That right flank has been where Liverpool have been the most exposed, with 38.1% of attacks coming down that third.

Frimpong and Bradley are both full-backs who like to push forward, but that means they often leave space behind that is exploited during counter-attacks, while Salah's lack of involvement in tracking back leaves them even more exposed.

Chelsea's winner against Liverpool on 4 October was the result of an overload down that side, while it was Szoboszlai who, after dropping into the right-back role, allowed Matheus Cunha to run in behind and earn the corner that led to Manchester United's winner on Sunday.

"The right-back situation is a mess," former Premier League striker Chris Sutton said on BBC Radio 5 Live's Monday Night Club.

"Szoboszlai has been their best midfielder, so playing him there kills him. And Frimpong, I don't care what anyone says, how can you spend that money on a right-back who can't really play there? It's bonkers."

Former Reds full-back Warnock said: "Conor Bradley was always going to be first-choice this season.

"But he is inconsistent. People will understand now how good Trent was and how consistent. Frimpong was signed as a utility player, not a defender. He is not a defender."

There have also been changes on the other side of Liverpool's defensive line, with Andy Robertson demoted to second choice after left-back Milos Kerkez's £40m arrival from Bournemouth.

Kerkez's defending has also failed to impress, with the eager Hungarian drawn out of position on countless occasions, leaving centre-back Virgil van Dijk exposed.

Does Robertson deserve another chance? And who is the best fit at right-back?

"Kerkez has not been an upgrade on Andy Robertson and Slot is unsure on what his best XI is," said Sutton.

"Defensively I am concerned about Liverpool."

With the full-backs struggling, it leaves more work for Van Dijk and Ibrahima Konate in the centre.

And they too have looked vulnerable, especially against speedy counter-attacks, while balls played in behind have presented problems to Liverpool.

At this stage of 2024-25, Liverpool had let in just three goals in the Premier League. That number has rocketed to 11 this time around, which is five more than promoted Sunderland have conceded.

Liverpool have also managed just two clean sheets so far this term and set-pieces have become a major worry for Slot's men.

They have let in five goals from dead-ball situations, with only struggling Nottingham Forest (six), Leeds United (six) and West Ham (eight) surpassing the Reds.

Individual mistakes have been costly too. Konate has looked unconvincing with the ball at his feet and was at fault for both Bournemouth goals in their season opener, while Van Dijk was drawn well out of position as United scored their first goal on Sunday.

How can Slot tighten Liverpool's backline before it costs them even more goals and points?