Giggs and the QPR boss were team-mates at Old Trafford and won two Premier League titles together before Hughes moved to Southampton in 1995.
The Loftus Road outfit are in 17th place – above the relegation zone on goal difference – but despite QPR’s lowly position, Giggs insisted United have no room to be complacent following the Hoops’ recent victories over Arsenal and Liverpool.
“Mark’s managed quite a few clubs now so he’s not a new manager anymore,” Giggs told United’s website.
“He’ll have them well drilled and well prepared, just like the majority of teams that come to Old Trafford. They’ll make it difficult for us.”
The 38-year-old added: “Hughes is a fighter and he has good staff around him. He made some good signings in the January transfer window and has a lot of quality in the side.
“QPR will be organised on Sunday and he’ll have them working hard.”
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news