The Red Devils spent more than £150 million on new players in the summer and brought in an array of attacking talents such as Angel di Maria and Radamel Falcao.
Yet, United have so far this season failed to put teams to the sword despite their impressive recent run of five victories on the spin.
The majority of Louis van Gaal’s side’s victories this season have come as a result of dogged defending and sturdiness, rather than a performance full of attacking endeavour and sublime forward play.
The Old Trafford outfit have notched just 26 goals in 15 matches – an average of 1.73 per game – which is far shorter than the Reds’ average of 2.65 goals per match last season.
Still, it seems only a matter of time before it clicks and Redknapp believes as a result of the Anfield outfit’s deficiencies in defence this season, it could certainly turn ugly on Sunday should the home side get it right.
“United have spent a lot of money and if they weren’t in the top four you’d have to ask questions, but with the start they’ve had they should really be closer,” he explained to Sky Sports.
“They’re not playing to the level they can but five wins on the spin is impressive, no matter how you do it.
“I’m expecting a lot more from them and that’s a danger for Liverpool. Sooner or later United are going to click going forward and if it happens on Sunday it could be a bit of an ugly afternoon for Liverpool.”
Brendan Rodgers’s side go onto the match lying in ninth spot in the table and coming off the back of a disappointing Champions League exit in midweek.
Defensively they have been at sorts all season and a repeat performance of their recent 3-1 defeat Crystal Palace could see them suffer a humiliating afternoon at Old Trafford.