Van Gaal is expected to be unveiled as David Moyes' successor next week after United relinquished their league crown with a seventh-place finish this season.
The outgoing Netherlands head coach will be tasked with bringing UEFA Champions League football back to Old Trafford with a top-four finish.
"The club needs a strong man to steer us back up,' the 50-year-old told the Daily Express.
"We have finished seventh, so the top four is a good target to set yourself for next season.
"But Van Gaal will not want to accept the top four - he will try and win."
"United have got (Phil) Jones, (Chris) Smalling and (Jonny) Evans but going by what the media are saying, Hummels is a target," the Dane said.
"That's a good starting point to bring him in. He has good leadership skills and he is a fantastic defender. He's someone we've been looking at for a couple of years and he's been heavily connected with United."
