Smalling was adjudged to have brought down Aleksandar Mitrovic in the box by referee Mike Dean at St James Park.
The Newcastle striker then stepped up to score his side’s second goal in the match. Smalling felt hard done-by following the clash.
“We were both jostling for positions throughout the game,” Smalling said.
“The referee said we were both at it so he didn’t give anything and I think there needs to be that consistency with the decisions. You can see my shirt was clearly pulled as well so it’s just about consistency. If you’re going to give them, fair enough, but you need to be giving them on a regular basis.”
There was an argument that it wasn’t a penalty but the same could be said of United’s spot kick after Chancel Mbemba was adjudged to have handled the ball in the area.
It was unlucky but United should have made their own luck against Newcastle, with Jesse Lingard, Marouane Fellaini and Wayne Rooney all spurning good opportunities to take the game away from their opponents. The game was a dramatic one but United will need to quickly turn their attentions to Liverpool and Anfield on Sunday.