Kenny picked up his calf issue during Thursday’s 2-2 Europa League draw with Bologna, but Celtic’s striking options are bolstered by the return to training of Kelechi Iheanacho, who has not featured since limping off in the Premier Sports Cup final defeat by St Mirren last month.
“It might be a bit of a stretch to start him in a game at the moment, but at least he’s going to be available,” O’Neill added of the Nigeria international.
Hearts beat Celtic 3-1 at Tynecastle in October – Brendan Rodgers’ final match in charge – and triumphed 2-1 at Parkhead in December as Wilfried Nancy began his ill-fated tenure.
O’Neill handed over the reigns to Nancy having won all six of his domestic matches in a ship-steading spell following Rodgers’ resignation, and he has maintained that perfect record since returning to the club.
However, Hearts have been Scotland’s standout team this season and O’Neill knows how consequential the match could be in the title race.
“It’s going to be very big, no question about it,” he said. “If we get beaten, it’s a long way back for us.
“I think it’s not the end of the road, but nine points would be a lot to claw back in 15 games left.”
O’Neill hailed the work done by Hearts head coach Derek McInnes and expects a “fiery” reception on Sunday.
“Terrific, it’s really been brilliant,” he added when asked about Hearts’ season to date.
“I was nearly going to say they’ve taken advantages of Celtic and Rangers slip-ups, but that’s not the case. They’ve driven on themselves and it’s genuinely great credit to them.”
