The Red Devils were held to an uninspiring goalless draw with West Ham United at the London Stadium on Thursday night.
While Manchester United’s performance was uninspiring, the point was enough to wrap up second place in the Premier League table.
The Red Devils will take on bitter rivals Chelsea FC in the FA Cup final at Wembley later this month.
Jose Mourinho is looking to win his third trophy since taking over the reins at Old Trafford after Manchester United won the Europa League and the League Cup last term.
Former Arsenal star Merson is backing Manchester United to make light work of Watford at Old Trafford in their final Premier League fixture of the current campaign.
“You’d think Man Utd would put on a show but when you watch them play sometimes,” Merson told Sky Sports. “I think they’ll gear up for the FA Cup final with a comfortable win here, though.
“Watford have done their job – it’s great achievement by them to stay up with ease – but United should have too much.”
Manchester United haven’t won the Premier League title since 2013 when Sir Alex Ferguson won the top-flight crown for the 13th time.
The Red Devils lost 2-1 to La Liga side Sevilla in the Champions League round of 16 earlier this season.
Manchester United were 2-1 winners against Tottenham Hotspur in the FA Cup semi-final at Wembley thanks to goals from Alexis Sanchez and Ander Herrera.
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