The defender was the match winner as he notched his fourth goal of the season in the 2-1 win over St Mirren at Ibrox.
Thelo Aasgaard had put the Light Blues ahead, before Fernandez fired home from close range to double the lead.
The big stopper believes set-piece coach Scott Fry deserves plenty of plaudits for helping the side become more of a threat from set-plays.
Speaking to RangersTV, he said: “Scott always tells us in the second phase of set pieces to get around the back and I saw an opportunity and I did that.
“I tried not to put too much on the finish, so I was delighted to score.
“A lot of work goes into the set pieces every day at training. It is probably more work than people think.
“Even if we are not successful in training we still get opportunities to be successful. We try our hardest to get goals from set pieces.
“I think both of our goals come from the second phase. I am a big guy and I am a threat, so I know when the ball comes in I am a threat.
“We knew it would be a difficult game, but we are happy with the result and now we move onto the next one.”
Fernandez was partnered beside John Souttar at the heart of the defence for the win over the Buddies.
It was the Scotland defender’s first start since a 3-0 win over Dundee on November 9 and Fernandez says it is a pleasure to play beside him.
He also praised No1 Jack Butland for saving Marcus Fraser’s penalty after Fernandez was judged to have handled a Conor McMenamin strike.
He added: “I like playing beside John and I am grateful to him. He talks to me all the time, everyone talks, but he leads me and keeps me on my toes, and it is a pleasure to play beside him.
“Jack bailed me out as I gave away the penalty. I am grateful to all the boys and to get all three points.
‘We are happy tonight, but we have to recover and go again on Saturday.
“We take it a game at a time, and we will see how we do in the second half of the season.”
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