The Red Devils signed Belgium international Romelu Lukaku in a £75m deal from Premier League rivals Everton in the 2017 summer transfer window.
Lukaku scored 16 times in his first Premier League season at Old Trafford as well as 10 goals in the Champions League and the FA Cup.
However, the 25-year-old striker was under pressure to perform on a weekly basis with a lack of support.
Manchester United haven’t won the Premier League title since 2013 when the Red Devils have proven goal-scorers such as Robin van Persie, Wayne Rooney and Javier Hernandez to count upon.
However, former England international Sheringham believes the Red Devils don’t need to sign a new striker this summer.
“They did just spend £70-80m on Lukaku so that’s a bit harsh,” Sheringham told BetStars</em>. “They’re missing the x-factor.
“They’ve got a lot of fantastic players and probably too many if I’m being honest. If you had half the players they’ve got, you’d work with them as a team rather than being a group of individuals.
“No one really knows what the formation is in each game and they’ll need to work on this for next season. You hope they aren’t just buying expensive players for the sake of it.
“Jose would say differently. There’s clearly something missing. They’re used to winning things and they need to get back to it.”
Manchester United finished in second spot in the Premier League table last term to secure their spot in the Champions League next term.
The Red Devils lost 1-0 to Premier League rivals Chelsea FC in the FA Cup final at Wembley after Eden Hazard’s winner from the penalty spot.
Manchester United have signed Brazil international Fred and Portuguese defender Diogo Dalot in the summer transfer window so far.
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