Before that, McIlroy, the 54-hole leader, was beginning to fade slightly from view. But the eagle moved him from 3 back to 1 back of then-leader Rickie Fowler. Three holes later he would be tied for the lead. Four holes after that, he'd own a 2-shot advantage.
McIlroy is now in a race against legacies. That's enthralling stuff. But so was Sunday's race against the darkness of a Louisville night.
The PGA of America couldn't do anything about the early afternoon rains that turned Valhalla Golf Club's fairways into rivers and the bunkers into wading ponds. However, it could have done something about its starting times, but didn't. Instead, the nearly two-hour rain delay caused a controversial finish when McIlroy and playing partner Bernd Wiesberger, the final pairing of the day, speed-golfed into Fowler and Mickelson on the 18th hole.
Had the tee times been moved up an hour, there wouldn't have been this silliness. It made for great TV, but the PGA of America's miscalculation put Fowler, Mickelson and McIlroy in an awkward and unfair position.
And yet, Mickelson almost chipped in for eagle on the par-5 18th. And McIlroy hit his second shot into a greenside bunker, and left his third shot 34 feet from the pin. If he doesn't two-putt, there's a Monday playoff.
And even more drama.
This was a PGA Championship -- and a winner -- that should make you a believer in the future of the game. The leaderboard was a gift from the heavens. There were so many quality storylines that you needed a spreadsheet to keep track.
Mickelson could have won his sixth major. Fowler and Henrik Stenson, who finished 2 shots behind, could have won their first.
Forty-four-year-old Ernie Els shot a 6-under-par 65 and squeezed his way into the conversation.
There were Ryder Cup implications.
There was everything. And there will be more.
Can April come fast enough? McIlroy will be going for the career Grand Slam when he arrives at Augusta National next year. Woods will presumably be healthy. Mickelson experiences a golf renaissance every time he drives down Magnolia Lane. Bubba Watson will be going for his second consecutive green jacket and his third in four years.
These are good times for golf. Even if everyone doesn't realize it yet.