United are keen on signing the England and Borussia Dortmund sensation in the next transfer window in a deal that could cost them up to £130m.
But Heskey told GentingBet: "When you look at Jadon Sancho's age, he will always be an asset to Liverpool.
"In two to three years, you've got an ageing Liverpool side - even though in this day and age and with the fitness levels of all the players, age is nothing.
"But having someone young, fresh and dynamic coming in, it will only add to the squad and I think that is where Jurgen is going to be looking at next. What can he add to the squad that is going to give Liverpool that little bit more longevity.
"When you look at the Liverpool frontline, you've got (Sadio) Mane and (Mo) Salah as the goal-getters and that is exactly what they do well.
"They command respect from defenders as a result. You'd like to think that Sancho has the quality to get in the side, but it will be very tough to get in ahead of Salah or Mane."