The Belgian scored the winner in a 2-1 victory for United over the MLS side in the second game of the US pre-season tour.
Asked about Lukaku's goal, the Basque midfielder told MUTV: "A fantastic goal! He didn't get in a panic, he was very calm. It was a fantastic goal.
"He is going to score a lot of goals for us but I want to speak about the work he does, always holding the ball up, he's very strong, it is very difficult to win the ball back against him so he is very important for us.
"We have a lot of players like Marcus [Rashford], Anthony [Martial], Mkhitaryan, they can do one v one but we needed one like him - strong, who can hold the ball for us. Sometimes when you are defending for a long time you can kick the ball forward and he is there to hold it for you so the work he does for us is massive."