Johnson returned to Royal Greens Golf & Country Club early Saturday to complete his second round and rolled in a birdie putt from 15 feet at the last for a 6-under 64, leaving him a shot off the lead shared by Fox and Stephen Gallacher.
Johnson moved into a share of the lead by the second hole of his third round and the outright lead by the time he reached the back nine. He brought the field back into play, though, by making a double bogey at No. 13 — for his first dropped shots of the week — after a poor 8-iron approach shot from the middle of the fairway that fell 30 yards short.
He reacted by finishing birdie-birdie — his eagle putt at the last shaved the right side of the cup — to take command again.
"I was a little frustrated today. You know, I just try not to let it linger too long," Johnson said. "I know I'm doing things right, but sometimes it just doesn't go your way.
"But I still played a really solid round and real happy with the way I'm playing," he continued. "A little frustrated maybe with the shot on 13. But other than that, very pleased with how I played."
The Saudi International is the last of three events in the "Gulf Swing" that launches 2021 on the European Tour.