Rickie Fowler and John Senden are through to the last 16 at the WGC-Cadillac Match Play Championship, after Thursday's second group matches.
Senden (2-0) dealt Bill Haas a 4-and-3 result to ensure his progression at TPC Harding Park, while Fowler's 1-up win over Shane Lowry guaranteed his berth in the last 16, as he moved to a 2-0 record in Group 13.
Henrik Stenson's 3-and-2 triumph over Brendon Todd was not enough to keep him alive as Senden cannot be passed atop Group 3 due to head-to-head records.
Fowler cannot be caught at the top after a 1-up win over Shane Lowry, as he has the tie-breakers on each of Lowry (1-1) and Harris English (1-1) with the latter beating Graeme McDowell 2-and-1.
No less than seven of Thursday's 32 matches went to extra holes, with each of Brooks Koepka, Webb Simpson and Charl Schwartzel moving to 2-0 records in thrilling fashion.
Koepka trailed from hole two through 17 in his match-up with Marc Warren, but somehow came out on top after 20 holes.
Three down with three holes to play, Koepka benefitted from two Warren bogeys before he birdied the 18th to extend it - and claimed victory on the second extra hole.
Similarly, Simpson never led Jimmy Walker - but an eagle at 18 kept him alive, and a birdie on the first extra hole saw him remain unbeaten.
And Schwartzel's victory was just as brave, as he defied the odds to beat Dustin Johnson after 20 to top Group 8.
Johnson was three-up after 11 holes, before Schwartzel had to eagle the 12th just to take a hole as Johnson made birdie.
The American led all the way from the third until the 17th, but a Schwartzel birdie on 18 took it to additional holes - and the South African completed the comeback with a birdie on the par-three second.
World number one Rory McIlroy got the better of Brandt Snedeker with a 2-up result, and he will take on Billy Horschel in a winner-takes-all battle in Group 1 on Friday after the latter eclipsed Jason Dufner 3 and 2.
Bubba Watson's clash with Louis Oosthuizen in Group 4 is another do-or-die battle, after the pair remained unbeaten.
Watson downed Keegan Bradley 4 and 2, while Oosthuizen was a 2-up victor over Miguel Angel Jimenez.
Group 2 leader Jordan Spieth continued his momentum with a 4-and-3 victory over Matt Every, while Charley Hoffman is setting the pace in Group 7 after a 2-and-1 result over Zach Johnson.
Other winners on Thursday included Justin Rose, Marc Leishman, Hideki Matsuyama, Kevin Na, Matt Jones, Paul Casey, Chris Kirk, Gary Woodland, Hunter Mahan, Matt Kuchar, George Coetzee, Thongchai Jaidee, JB Holmes, Lee Westwood, Danny Willett, Andy Sullivan and Tommy Fleetwood.
Out of contention for the knockout stages are defending champion Jason Day, 2014 finalist Victor Dubuisson, former world number one Adam Scott and 2010 winner Ian Poulter.