Rory McIlroy and Paul Casey faced an early return to Harding Park to complete their quarter-final in the WGC-Cadillac Match Play after darkness forced play to be suspended on Saturday.
While Danny Willett, Gary Woodland and Jim Furyk all enjoyed comfortable victories to advance to the semi-finals, McIlroy and Casey could not be separated after 21 holes in San Francisco.
Casey was one up with two holes to play only to three-putt the 17th, while both players missed chances to win in extra holes before deciding it was too dark to continue.
"I dodged a couple of bullets but felt I gave him one or two," Casey said after McIlroy missed from six feet to win the match on the third extra hole. "I am glad we are teeing up tomorrow, simple as that.
"I thought I was done for the day and the week on this green. The beautiful thing is we hit the reset button, come back at 6:45am and start again.
"We looked at each other on the 15th (the second extra hole) and said 'One more'. It really was dark, whatever the TV cameras are showing and both of us agreed."
McIlroy added: "I made a couple of key up and downs when I needed to coming down the stretch. I had a couple of opportunities to close it out, one on 18 and one there and could not quite convert.
"It was getting pretty dark so we come back in the morning and try again."
McIlroy or Casey will take on Jim Furyk in the last four after Furyk defeated JB Holmes 5&3 in the last 16 and then Louis Oosthuizen 4&2 in the quarter-finals.
The other semi-final was between England's Danny Willett and American Gary Woodland, with Willett beating compatriots Lee Westwood and Tommy Fleetwood, while Woodland defeated Australian pair Marc Leishman and John Senden.
McIlroy had earlier thrashed Japan's Hideki Matsuyama 6&5 in the last 16 and was hoping another comprehensive win might have allowed him enough time to get to his ringside seat for the contest between Floyd Mayweather and Manny Pacquiao.
However, after losing the first to a McIlroy birdie it was Casey who moved two up thanks to birdies on the fourth, fifth and seventh, and although McIlroy got back on level terms, the 25-year-old then bogeyed the 14th to give Casey the upper hand.
Casey was unfortunate to see his tee shot on the 17th finish up against the collar of rough around the green and the resulting three-putt allowed McIlroy to get back to all square after he saved par from right of the green. Neither player was able to birdie the par-five 18th and the match went into extra holes, starting on the 14th.
Both players got up and down to save par on the 14th before Casey left a birdie putt agonisingly short on the 15th, but McIlroy missed from just five feet on the 16th before play was halted.
Westwood later posted a picture on Twitter of himself and Ryder Cup captain Darren Clarke at the fight, and Willett explained: "If all would have gone terribly wrong today, I would have been going.
"But Lee has got the ticket. Basically it was either me or Lee was going to go. It's going to be a good fight. A shame to miss it. But for me it's obviously good being here."
And the European Tour also posted a picture showing McIlroy giving the thumbs down sign as he had to settle for watching the fight in the media centre at Harding Park.