The 42-year-old is still a favourite amongst Chelsea supporters, with a banner being unfurled during the match against Hull last Saturday calling for his return.
He left in June 2007 after two promotions had seen the Tigers climb to the Championship and, following his departure from Derby, has been linked with a return to the KC Stadium with the future of Hull chairman Paul Duffen in doubt.
The company said management at its Hull factory had "proposed improvements in basic pay and no redundancies in return for the continued suspension of premium pay for overtime and bank holidays".
But the Swans and Hull took time to thrash a deal, and Duffy revealed he feared his chance to return to south Wales had gone when he joined the rest of the Tigers squad on the club's pre-season tour to Italy.