The two semi-finals at the WGC-Dell Technologies Match Play both went to the 18th, with Kevin Kisner and Matt Kuchar eventually progressing.
Rory McIlroy made it three wins from three on Friday, with Tiger Woods standing in the way of him and a quarter-final berth.
American Joel Dahmen and Austrian Sepp Straka – who are both seeking their maiden PGA Tour victories – ended the day a stroke clear.
There were almost two balls in the hole in quick succession when Patrick Cantlay's tee shot found the 12th green.
Gary Woodland remains the man to catch at Bellerive Country Club, where Brooks Koepka and Charl Schwartzel shot record-equalling 63s.
Kevin Kisner finished in a share of second place at The Open last month and moved into the lead in the final major of the year on Friday.
Francesco Molinari moved to the top of the European Ryder Cup points list with his historic victory at Carnoustie.
Seeking a 15th major title and first in 10 years, Tiger Woods surged into contention at the 147th Open Championship on Sunday.
Kevin Kisner's hopes of a maiden major win suffered an early blow, as Jordan Spieth and Tiger Woods got underway at The Open.
Only a few "horror stories" will be exchanged with Jordan Spieth before the last round of The Open, says Kevin Kisner.