The Carlisle United defender played with Mackie in both of the winger's Queens Park Rangers spells.
R's boss Ian Holloway announced via the club's website that Mackie - who is in his second spell at Loftus Road - will leave when his contract expires at the end of the campaign, alongside James Perch and Jay Emmanuel-Thomas.
And Hill - a teammate of Mackie on two occasions - posted on Twitter shortly afterwards:
What a character this fella is. Gave everything he had for the club and can leave with his head held high. Hopefully he will get a decent send off to. “Walkinginamackiewonderland https://t.co/u7xY8fYH7i— Clint Hill (@clinthill29) 6 April 2018
Defensive duo Nedum Onuoha and Jack Robinson could yet follow Mackie, Perch and Emmanuel-Thomas out of QPR, although the R's are in discussions with both players.
Onuoha was linked with a move to Burnley earlier this year, while Robinson is said to be a target for Sheffield United.
However, the Australian - who has scored or made nine league goals this season - still has two years left on his Loftus Road deal.