Thankfully they've got just the man for the job when it comes to finding the net against a Premier League new boy.
By his own meteoric standards, Cristiano Ronaldo perhaps hasn't hit the exquisite levels that have previously established himself as one of the best players in the history of the game.
Four goals in eight Premier League appearances and nine in 13 overall certainly isn't bad, but after drawing blanks against Liverpool and Manchester City it means that he'll be looking to get his scoring boots back on at Vicarage Road this weekend.
It's safe to say that his record against newly-promoted teams means it would take a brave person to bet against him doing exactly that.
Since the 2003/04 campaign, Ronaldo has been directly involved in 104 goals in 91 league appearances against newly-promoted teams (83 goals, 21 assists), scoring or assisting every 71 minutes on average.
That record is even more impressive of late, with the 36-year-old scoring 20 goals in his last 14 league matches against promoted teams during his spells with Real Madrid and Juventus.
With Watford winning just one of their last six Premier League games and conceding 19 goals in total so far this season, the hope for Manchester United and Ronaldo will be that he can continue this stunning record against Claudio Ranieri's side.