Riether was not punished for his actions by referee Lee Probert, which came in the last minute of Fulham's 3-1 defeat to United at Craven Cottage on Saturday, but on the face of it it did look like the type of incident new Football Association chairman Greg Dyke wants to clamp down on.
"For me it was a red card for the right back," the Belgian told MUTV.
"I hope the referee looks at the video later."
United manager David Moyes was more philosophical as his team extended their unbeaten run.
"We are never going to ask for (protection)," said Moyes.
"We want him to get up. We don't want him to go down easily.
"He is a really honest boy and I thought there were a couple of times when fouls should have been given against him but they weren't."