Mauro Icardi (Inter Milan)
Serie A may not be the best league in Europe anymore, but it does remain the best place to see well-organised defences with a no-nonsense style and unique physicality, meaning any striker that thrives in that environment must be taken seriously.
One man who fits that bill is Icardi, whose record at Inter reads 110 goals scored in just 188 games over the last five years of his career.
The Argentine striker has hit the ground running again at the start of the 2018-19 campaign, most notably producing a match-winning performance against Spurs in the Champions League back in September and his eye for goal has earned him attention from a whole host of clubs around Europe.
According to the Daily Express, Chelsea and Barcelona are interested in pursuing him in 2019, but United could enter the race for his signature if Lukaku continues to struggle.
Icardi would likely cost the Red Devils a huge sum of money, but he has the credentials to be an instant hit at Old Trafford and he is only going to improve as he approaches his prime at 25 years of age.