While most of the 156-strong field elected to take a more conservative approach, striking irons off the tee for accuracy and to gain better control of balls that were bounding down the fairways, Rahm opted to use the longest club in the bag.
Asked by reporters if he felt his strategy had succeeded, the beefy world number five replied: "You tell me. Did it work?
"I would say it was pretty successful. I don't feel like I was overusing the driver. It's just there are some holes where the rough is so thin that if you can carry a certain distance (with an iron), it's almost as bad as driving.
"If you're in the rough you have a wedge in and if you're on the right side of the rough you actually have an easy shot to make it certain yards away. I don't think I could have played any better off the tee really," said Rahm.
"I had an understanding of when I could hit driver. When the pin is back left and back right, and the wind is down, and the driver, if you could carry it 300 yards, was beneficial."
Rahm mixed four birdies, including a sequence of three in four holes on Carnoustie's front nine, with two bogeys to tuck himself in three strokes behind clubhouse leader Kevin Kisner of the U.S.
The 23-year-old Rahm, who is almost certain to make his Ryder Cup debut for Europe in Paris in September, is undecided whether to continue with his tactics on Friday.
"It all depends where the pin positions are," he said. "When you get to the tee you look at the wind and sometimes it's worth it to hit driver, sometimes it's not.
"There are too many bad spots to go where the risk is higher than the reward. There are a number of holes where I didn't hit driver today but maybe I will (tomorrow). You never know."
(Editing by Toby Davis)
