Martin O'Neill hailed the influence of Kelechi Iheanacho after Celtic roared back in extra time against St. Mirren to reach the Scottish Cup final.

Goals from Daizen Maeda and Anthony Ralston had Celtic cruising at 2-0 up on Sunday, only for Mikael Mandron to pull one back in the second half.

Mandron grabbed his and St. Mirren's second in the first minute of stoppage time before Celtic blew away their opponents in the additional 30 minutes for a 6-2 win.

Iheanacho found the net twice in extra time, along with finishes from Luke McGowan and Benjamin Nygren, and O'Neill picked out the Nigerian striker for special praise.

"Kelechi [Iheanacho] has had a great career," the Celtic boss said on Premier Sports.

"He has had injury problems. But he looks good, and he wants to do really well. I've praised him enough in the dressing room – I think he was quite surprised!

"Sometimes you question yourself when you don't get the result. Other than Tannadice, I've not had to question the spirit of the side."

Celtic will face Dunfermline Athletic in next month's final after this eight-goal epic at Hampden Park.

That means O'Neill will face former player Neil Lennon, in a repeat of the 2007 final, which Dunfermline lost 1-0 in their last appearance in the Scottish Cup final.

"Neil was a major player for us and his record in management is second to none," O'Neill added before reflecting on his extra-time message.

"We found something in extra time, and Iheanacho's goal turned it immediately for us again.

"We've all been there when you think you're saying something at the end of the game, but it's more encouragement for yourself than anything else.

"They were really deflated, but you have to go again. Scoring early on made a massive difference; the confidence was restored again.

"It's nice to play. I could have played when we were 6-2 in front at the end. My grandchild could have played. It's trying to get there."