Januzaj appeared to be deliberately stood on by Hull midfielder David Meyler in an unsavoury incident during the closing stages of United's 3-1 Premier League win at Old Trafford, leaving the attacking midfielder with visible marks on his leg.
Former manager David Moyes led the way in demanding protection for the 19-year-old during his brief 10-month tenure and now interim boss Giggs has joined the chorus in calling for action from the Football Association, who have the power to suspend Myler.
"I didn't see it, but I've seen his leg (with stud marks)," Giggs told reporters after the match.
"It's not great to see, it is terrible his leg. He needs protecting, he's a brilliant player, he's exciting, the authorities need to stamp down on it.
"I'm not sure what can happen now but it was bad, I didn't see the stamping but I've seen his leg and it's a joke.
"It's not broke the skin but it just goes from knee to his ankle."
Meanwhile, Giggs' playing future remains uncertain after the Welshman confirmed he would take time to think about the situation at the end of the season.
With Louis van Gaal expected to take the reins in Manchester, Giggs is in contention to join the Dutchman's backroom staff but his days as a player are still up in the air.
"Not decided yet, nothing's changed, just wait till the season's finished, get a holiday and then think about it in the next couple of weeks," he said.
