That Tannadice rush of blood to the head was a sign of the frustration that has been brewing under the surface for the Colombian amid a dry spell that stretched back to his last league strike against Hibernian in September.

But there were no cracks in his confidence this time as he coolly slotted past St Mirren goalkeeper Jak Alnwick following a poor Joe Shaughnessy back-pass to put Rangers two-up just six minutes after Kemar Roofe had scored the opener.

And Gerrard admits Morelos' return to form could not be better timed for his team as they look to stretch their 16-point lead over Neil Lennon's Hoops when they host the second Old Firm derby battle of the season this weekend.

"Alfredo will be delighted with the goal," he said. "He has been training well and I had a good feeling it was about to come.

"He's getting into some good places. He was unlucky against St Johnstone last week and unlucky against Hibs on Saturday when he came on.

"So I had a feeling it was only a matter of time. You can't keep him down forever. That will do his confidence the world of good."

But the Rangers boss admits he will be short on midfield options after seeing Arfield join Ryan Jack in the treatment room.

The Canada international suffered an ankle injury against Hibs on Boxing Day, and Gerrard said: "The scan came back and we are just waiting on a few more opinions on it.

"We've had one opinion on it and he will obviously be missing in the short term. He will definitely be missing for a few weeks, that's for sure.

"But in terms of the exact date or time, it's very difficult right now. He will certainly miss the next two or three fixtures."

Rangers were looking to avenge their only defeat of the season so far as they faced up to Saints just two weeks on from being dumped out of the Betfred Cup by the Buddies.

Roofe's strike deflected off Conor McCarthy to leave Alnwick with no chance, while the keeper was exposed again when Shaughnessy's mistake played in Morelos.

But Gerrard admitted: "I don't think we showed our best style in terms of possession and creation but we've won the game comfortably.

"There are a lot of positives to take from the game, from individuals playing well within it.

"But there were patches which were a bit scrappy and a bit ugly as well. We came here to do a job, we came here for three points and we've done it.

"It was another strong performance from Glen Kamara and from Joe Aribo. We've got players in a good place. Ianis Hagi has contributed again with an assist.

"It's another clean sheet as well. So there are a lot of pleasing things. But in terms of how it looked on the eye, in terms of style, it was very patchy."

Saints boss Jim Goodwin said: "I'm disappointed to lose the game. The first goal I couldn't really point the finger at in terms of blame.

"We spoke about those quality runs that the Rangers players can make, but Conor McCarthy has matched Roofe all the way and got half a block in but unfortunately Jak Alnwick was going the other way and couldn't get to it.

"Rangers deserved to win the game because they took that first opportunity and the second goal was a howler from us. Ultimately, Rangers scored a couple of goals and that's why they won."