Rashford, playing in his first Manchester derby, scored what proved to be the winning goal in the 16th minute as Man United secured a big three points in the race to finish in the top four of the Premier League.
Smalling was full of praise for Rashford following the clash.
“It is so refreshing to see a young kid like Marcus run at defenders, I know if I was up against him I would find it difficult,” Smalling said.
“It was difficult for me today as I got an early booking and I had to be more careful and a couple of times pull out of tackles but I managed it.”
Rashford showed composure and class which belied his years against City and it was fantastic to see a Manchester-born player decide the derby.
Wayne Rooney will soon return from injury but he will have a fight on his hands to get back in the starting XI over Rashford. The 18-year-old’s emergence has been a huge positive for United this term.