Duff withdrew from the Irish squad yesterday due to injury and returned to Fulham for treatment, but he is hopeful of being fit again for Andorra's visit to Dublin next Tuesday.
"I spoke to Damien and he's upset at missing the game," said Kelly. "He hates missing any match but it really gets to him when he has to miss an Ireland game. It was a massive blow for him to come over and then have to go home again, but we'll see what happens. He came off before the end of Saturday's game and he wasn't too sure what had happened, whether it was a tear or just a niggle.
"He recovered well the last time he was injured, so fingers crossed the treatment goes well and he can come back in for the Andorra game next week. He's back at Fulham now and getting treatment, he'll be in the oxygen tent but he will be doing all he can to get fit -- maybe for the second game next week."
Galway cup win seals Rovers tie
Airtricity Premier Division leaders Shamrock Rovers will face Galway United in the FAI Ford Cup quarter-finals.
Galway were 3-1 winners over Salthill Devon last night, while holders Sporting Fingal beat Limerick 4-3 on penalties after a scoreless draw at Jackman Park.
Fingal will face Dublin rivals St Patrick's Athletic at Richmond Park, league champions Bohemians have been drawn at home to Bray Wanderers and Sligo Rovers will host Monaghan United at The Showgrounds.
The quarter-finals will be played over the weekend of September 18/19.
FAI Ford Cup Quarter-Finals
Bohemians v Bray Wanderers
St Patrick's Athletic v Sporting Fingal
Shamrock Rovers v Galway United
Sligo Rovers v Monaghan United