Garcia shot 3-under 67 to go from a three-shot deficit on the front nine to a three-shot lead through 54 holes, leaving him poised to become only the third player to capture The Players Championship and the Tour Championship in the same year.
Garcia was at 8-under 202 and will play in the final pairing today with Phil Mickelson, who made some long par putts and just enough birdies for 69, giving him a chance to end his year on a strong note.
Six days after Kim crushed Garcia in the leadoff singles match at the Ryder Cup, the 23-year-old American looked as if he would get the best of Garcia again with six consecutive one-putt greens. But Kim hit only four fairways, and his wildness caught up with him.
"I don't know anyone that could have fixed that golf swing," Kim said. "I was just trying to hit it in the right areas of the rough."
The worst of it came on the ninth, when his tee shot hit a 48-year-old man in the forehead on the fly, opening a 2-inch gash that spilled blood on the Bermuda rough. The fan, David Whitfield. of Atlanta, was taken to a hospital, but he never lost consciousness and appeared to be in good spirits.
Kim gave the man's wife a golf ball that he signed with a note: "Sorry."
Garcia birdied the par-5 ninth to catch Kim, and pulled away with a birdie on the par-5 15th.
"Obviously, AK wasn't on his A-game," Garcia said. "I still feel like he scrambled nicely. He got some putts going in the beginning. I managed to make some birdies and played solidly."
Kim wound up with 72 and was three shots behind.
Those two young stars in the final group of the third round finally brought some energy to the post-Ryder Cup blues at East Lake, although anyone hopeful of a rematch would have been sorely disappointed.
They were laughing and chatting from the start, especially on the first green when Garcia asked if he should move his ball mark.
"He gave me one of those looks like, 'I don't need to hit it that far left.' And he actually hit the left side of the coin," Garcia said. "It was one of those funny things that happen."
Mickelson, who saved par from 35 feet on the 11th, briefly joined them in the lead with a birdie at the 15th, only to miss the fairway into thick rough on the next hole and drop a shot.
Even so, he has been lurking around the leaders all week and worked his way into the final pairing on a course where he won in 2000.
"It's fun to be in the last group," Mickelson said. "I'm looking forward to it. I know it's going to be difficult. I'm spotting Sergio three shots. I know how well he's been playing, so it'll be a difficult round for me to get it done."
Camilo Villegas had 69 and was at 3-under 207, while Ben Curtis (68) and Robert Allenby (67) were another shot back.