Arne Slot isn't just hoping his marquee signings will step up against the Premier League's elite. He's certain they will.

Florian Wirtz and Alexander Isak cost Liverpool a combined £241million when they arrived at Anfield, but their impact against top-tier opposition remains a question mark heading into Sunday's Old Trafford showdown.

Wirtz, who became the club's record signing at £116million from Bayer Leverkusen before Isak's British record £125million arrival from Newcastle surpassed that figure, has delivered seven goals and 10 assists this season. The catch? None have come against teams currently in European qualification positions.

That could all change with three massive fixtures on the horizon. After facing Manchester United, Liverpool still have Chelsea and Aston Villa to play, giving the German international ample opportunity to silence his critics.

"I don't only hope that, I am 100% sure he will," Slot declared when asked about Wirtz's record against leading teams. "For me it is a coincidence, we have to play three more who are in those positions so that gives him three more chances to do this."

The Reds boss has watched Wirtz transform during his 10 months on Merseyside, pointing to last weekend's display against Crystal Palace as evidence of the 22-year-old's evolution.

"The development Florian has made throughout his Liverpool career, which has only been 10 months, is so clear and obvious: 93rd minute against Crystal Palace making a duel on the sideline, winning a throw-in and then making a sprint from 40 yards and hitting the ball in the top corner, that is something I am not completely convinced he could do the same eight months ago," Slot explained.

For Slot, this is just the beginning. Wirtz's age works heavily in Liverpool's favour, with the manager convinced the German will only improve as he approaches his peak years.

"His improvement - and he was already an elite player – has been, for me, clear and obvious and that improvement will only continue as he is only 22 so that makes complete sense," Slot noted. "Almost every player in the world is at his best when he is 25, 26 but he is already an elite player now and he can only become better and that is the beauty of the signings he did last summer, that all of them are of a certain age where we can only expect them to get better – as long as they don't get injured."

Whilst Wirtz has been finding his feet, Isak's availability has been the bigger concern. The Swedish striker has started Liverpool's last three matches and could play four consecutive games alongside Wirtz for the first time since his arrival.

Liverpool's struggles in front of goal this season tell their own story. Despite registering the most shots in the Premier League, they've scored 23 goals fewer than at this stage of their title-winning campaign last season. Slot believes Isak's presence can change that narrative.

"Having Alex more and more available, having him available at his top level, would increase that even more," the manager said when discussing Liverpool's conversion rate. "In general having players available would help becoming consistent; at the moment not playing three times in seven days helps in our consistency."

Isak's improvised opener against Palace demonstrated exactly what Liverpool have been missing. It wasn't their best chance of the season, but the striker's clinical finish showed the difference a natural goalscorer can make.

"Last week you could see it was a chance but it wasn't the biggest chance we've had this season and he finished that one off really well by scoring the 1-0 and scoring a goal which is vital in football as it sets you in the right direction or if you don't score it and concede a set-piece at the other end – which happened so many times in the first half of the season – that brings the game in a different direction," Slot explained.

With the manager acknowledging that other players haven't reached their expected goal tallies, Sunday's trip to Old Trafford represents more than just three points. It's a chance for Liverpool's expensive acquisitions to prove their worth when it matters most.