The 20-time English champions finished in second place in the Premier League table last season ahead of the traditional rivals Tottenham Hotspur, Liverpool FC, Chelsea FC and Arsenal.
Manchester United, though, didn’t come close to eventual champions Manchester City after Pep Guardiola’s men finished a comfortable 19 points ahead of their derby rivals.
Mourinho spent £52m on Shakhtar Donetsk midfielder Fred, Portuguese teenager Diogo Dalot in a £17m deal from FC Porto before veteran goalkeeper Lee Grant completed a move to Old Trafford.
However, the Red Devils missed out on some of Mourinho’s key targets to leave the Portuguese head coach short on options ahead of the new Premier League campaign.
Former Arsenal star Merson believes Manchester United will finished in third place but doesn’t expect the Red Devils to challenge for the Premier League title.
“Manchester United are a long way off, but I think they’ll be third. This season, it just doesn’t seem a happy camp,” Merson told Sky Sports.
“The manager doesn’t give that aurora of excitement and thinks he might have bitten off more than he can chew. I think by Christmas it’ll be ‘watch this space’. They’ll either be top, which I can’t see, or that’ll be it.”
Manchester United will start the new Premier League season with a home clash against Leicester City on Friday night.
The Red Devils haven’t won the Premier League title since Sir Alex Ferguson’s retirement in 2013.
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