American Matt Kuchar missed out on the outright lead after bogeying the final hole in the penultimate round of the Memorial Tournament in Ohio.
Kuchar, 37, winner of the event in 2013, had gone ahead with four birdies in five holes from the 11th but found a bunker off the tee at the last.
He carded a two-under-par 70 to share the lead with compatriots William McGirt and Gary Woodland on 14 under.
World number one Jason Day is three back, with Rory McIlroy five adrift.
Day, who clinched his third PGA Tour victory of the season at the Players Championship last month, had moved to within one of the lead but his chip at the 18th rolled back past him into the fairway and resulted in a double bogey for a round of 68.
Journeyman McGirt, bidding for his first PGA Tour victory in his 165th career start, put himself in contention with three birdies in the closing five holes in a 64.
Play was suspended for two hours, 29 minutes because of bad weather, but resumed just in time for the final groups to complete their rounds before darkness fell at Muirfield Village.
Thunderstorms are forecast for Sunday afternoon, prompting tournament officials to send the players off in threesomes in the final round.