City secured the £1.5m capture of the Gabon international with just hours to go before the transfer window closed on Sept 1.
And McKay today said Duffen's ability to conduct the negotiations with the player in his native language had been key in securing the deal.
"Paul Duffen did a great job to get Daniel" the Scottish agent told the Hull Daily Mail. "Lots of clubs in France and England were coming in for him. Fulham also came in and Wigan and Stoke wanted him.
"But one of the major factors was the fact Paul Duffen spoke fluent French, which was a big help as he speaks French like a machine gun. To be honest with you, it's great when you've got a chairman who is as hands on as Paul Duffen is."