United were furious after the game, and indicated they would make a formal complaint to referees’ body Professional Game Match Officials (PGMO).
The Red Devils’ issue was around consistency, with two other penalties awarded in the game for holding offences.
Manager Michael Carrick described the decisions as “baffling”, confused that Attwell’s decision did not match an earlier spot-kick given to his side for a pull by Alex Jimenez on Matheus Cunha.
“So the Cunha one, he gives, the second one on Amad he doesn’t, which is, I think, almost identical, really, two hands on someone in the box, and they go over and they’re in control of the ball,” Carrick said.
“Massive moment and I don’t understand how you can give one and not the other -…