Wayne Rooney’s second-half goal handed the Red Devils victory at Anfield and kept Louis van Gaal’s men two points behind fourth-placed Tottenham Hotspur as the race for Champions League qualification hots up.
The defeat left Liverpool in ninth place in the Premier League table and eight points behind Spurs.
Jurgen Klopp has been tasked with steering Liverpool back into the top four after the German coach was appointed as Brendan Rodgers’ successor on Merseyside back in October.
Souness feels that the Reds are capable of finishing in the Champions League places but admits he is worried about Liverpool’s lack of attacking threat.
Speaking on Sky Sports after Sunday’s game at Anfield, Souness said: “For me, I think they can still make the top four.
“I said at the start of the season, Liverpool don’t have a free-scoring midfield who will chip in with two or three goals each.
“For Liverpool to get into the Champions League, they need Christian Benteke to get well over 20 goals because you can’t trust Daniel Sturridge – he’s exceptionally talented but doesn’t play enough football.
“So you’re relying on Benteke staying fit and scoring goals and carrying them into the top four. I don’t see where the other goals are coming from and in this league you must always be scoring goals.”
Liverpool host Exeter City in their FA Cup third-round replay on Wednesday before a trip to Norwich City next weekend.
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