Both Glasgow giants square off in the semi-final of the Scottish Cup on April 17 for what will be just the second Old Firm meeting since Rangers were demoted to the fourth tier in 2012 after being liquidated.
Victory is anything but a foregone conclusion for Celtic despite literally being a league above Mark Warburton's troops, who sit top of the Scottish Championship by 11 points - with a game in hand - as a return to the top flight seems imminent.
Duffy, the Greenock Morton boss, says the Championship is rich with quality, but warns Warburton that his defence will not have come up against anything like Griffiths before, with the hitman boasting 33 goals in all competitions.
"Although there are some good players in this division, you don't come up against players with the quality of Leigh Griffiths," he said to the Glasgow Evening Times.
"If Rangers do push the full backs on, Griffiths will thrive in that space. Mark Warburton has stated quite publicly that he won't change his philosophy so that will be a test of that statement."
Celtic have been somewhat laborious in recent weeks despite being top of the Scottish Premiership, but a last-minute winner at Kilmarnock on Saturday opened up a four-point gap from second-placed Aberdeen.
With the Hoops making hard work of what has been a one-horse race in recent years, it remains to be seen if manager Ronny Deila will survive the summer, but defeat to Rangers might well make the decision a whole lot easier for the club's board.