Saints rarely looked capable of securing a first win of the campaign but midfielder Murray Davidson thought he had grabbed a late lifeline before Davis scooped the ball into the hands of goalkeeper Allan McGregor. Defoe then swiftly notched his first goal to put the result beyond doubt.

"People will talk about the goal-line clearance but from the angles I've seen it's not a goal," Gerrard said.

"It wasn't a goal. Steven did well on two occasions and I thought he was man of the match by some distance. I thought he was outstanding.

"The linesman deserves credit for getting that one right because it could have been a big moment.

"It could have put us under pressure late on but with our all-round application I felt we thoroughly deserved the clean sheet."

Gerrard was delighted to see his side going through the gears after the interval.

"First half we did OK and got into some really good areas. But we didn't have much quality and it wasn't connecting in the final third. That was why we didn't create," the former England midfielder said.

"We had one good chance with Alfredo but we need to try to create more.

"After the break we found our level of performance. We were outstanding in the second half."

Morelos fired Rangers ahead with his 12th goal of the season and Gerrard is hoping his talisman has cleaned up his act after last season's disciplinary issues.

"Alfredo deserved that goal for his endeavour and desire. Against a different type of opposition on Thursday against Feyenoord he was unplayable.

"He's in good place, he's enjoying his football and he's behaving himself. He was even shaking the referee by the hand on the way off so he's definitely trying!

"He's a match-winner and I'm really pleased with him.

"His overall game was top drawer and it's why he's been called into the Colombian squad (for next month's friendlies). I hope he gets selected."

Saints manager Tommy Wright saw the Davis goal-line clearance in a different light.

"We tried to stay in the game and we think we got a perfectly good goal. We didn't get it and they went up the field and scored," he said.

"You think it is going to be 2-1 but it is 3-0 and game over. We think it is over the line, I know Rangers are saying it wasn't.

"My first impressions were that it was over the line. If we had VAR, it would tell us one way or another.

"And the fourth goal was well offside. I don't know how the linesman doesn't get it – that was poor.

"But refereeing decisions aren't what cost us the game – it was our poor decision-making and poor defending.

"For their third we had too many players arguing with officials and they went up the field and scored. That is naive, just get on with the game.

"Rangers deserve their win. My frustration is not with the officials but some of our defending at times."