St Johnstone manager Tommy Wright feared floodlight problems would halt his side's William Hill Scottish Cup progress before seeing out a 3-0 triumph over Morton.

Problems were evident for much of the first half at McDiarmid Park and the second half was held up for almost 25 minutes after they went off completely.

Wright revealed how near referee Nick Walsh came to abandoning the game with Saints 1-0 up through Callum Booth's spectacular early opener.

"It was close," Wright said. "I think he was giving it three more minutes.

"Then your worry is, when you go two and three up, are they going to stay on or not?

"If they had have gone off...."

Morton started the second half well but Murray Davidson doubled the lead with a 57th-minute header from a corner before Stevie May raced on to a ball over the top to round off the fourth-round win.

Wright said: "Three quality goals and I think that was the difference, the extra bit of quality we had.

"After the winter break sometimes you don't know what you are going to get. The performance was good at times and patchy at others.

"Morton started the second half better than us and three or four moths ago we would probably have conceded in that time but we didn't, we won our headers and Zander (Clark) made a couple of saves from long range. We were solid and effective and there's a lot more to come."

Morton boss David Hopkin bemoaned missed chances from his team with Luca Colville and Robbie Muirhead culpable in the first half.

"When you play Premiership teams you have to take your chances, and we didn't," he said.

"Callum Booth will never hit a ball with his right foot again (like that). We came out after the delay and that 15-20 minute spell we have got to score.

"Murray Davidson is probably the best header of a ball in Scotland and we gave him a free header.

"They got two or three chances and they took them."