Simpson was influential in their 1-1 result at Old Trafford.
"I am keeping my head down," said the Salford-born defender. "I have already had a few texts from friends who are not very happy.
"There was a bit of banter with the players at the end, with them telling me I had spoiled their day.
"United are quality. When you look at the chances, people might ask why they didn't win the game.
"You can see why they score so many late goals. They are so clever.
"Even with the offside, it was a relief."