Rory McIlroy and Paul Casey could not be split after 21 holes as darkness halted their quarter-final in the WGC Match Play in San Francisco.
They will return at 14:45 GMT (06:45 local time) to decide who will play American Jim Furyk in the semi-finals.
Casey, 37, was one up on the 17th before three-putting to allow Northern Ireland's McIlroy, 25, to level.
Casey's fellow Englishman Danny Willett, 27, faces 30-year-old American Gary Woodland in the last four.
Willett beat compatriot Tommy Fleetwood 4&3 while Woodland was a 5&3 winner over Australian John Senden.
Furyk, 44, beat South African Louis Oosthuizen 4&2 to reach the semi-finals.
After reaching the regulation 18 holes level, Casey and McIlroy both missed chances to win their tie.
"It really was dark, whatever the TV cameras were showing and both of us agreed," said Casey.
McIlroy had earlier beaten Hideki Matsuyama 6&5, wile Casey saw off former Masters champion Charl Schwartzel 2&1.
Saturday's quarter-final results
Danny Willett (Eng) beat Tommy Fleetwood (Eng) 4&3
Jim Furyk (US) beat Louis Oosthuizen (SA) 4&2
Gary Woodland (US) beat John Senden (Aus) 5&3
Rory McIlroy (NI) AS Paul Casey (Eng) after 21 holes
Saturday's last-16 results
Rory McIlroy (NI) beat Hideki Matsuyama (Jpn) 6&5
Paul Casey (Eng) beat Charl Schwartzel (SA) 3&1
Danny Willett (Eng) beat Lee Westwood (Eng) 3&2
Tommy Fleetwood (Eng) beat Branden Grace (SA) 2&1
Jim Furyk (US) beat JB Holmes (US) 5&3
Louis Oosthuizen (SA) beat Rickie Fowler (US) 1up
Gary Woodland (US) beat Marc Leishman (Aus) 2&1
John Senden (Aus) beat Hunter Mahan (US) 2&1