Defending champion Jason Day has pulled out of the WGC-Dell Match Play after just six holes due to the ill health of his mother.
The 29-year-old was narrowly behind to Pat Perez early on in Texas when conceding defeat, before officially announcing that he would play no further part as his mother had recently been diagnosed with lung cancer.
Fellow favourites Rory McIlroy and Jordan Spieth are themselves heading for an early exit, meanwhile, with the former - a semi-finalist here in 2016 - losing his opening match for the first time in five years.
Soren Kjeldsen fell three holes behind against the Northern Irishman but ended well to take the match, while Spieth lost to tournament debutant Hideto Tanihara after missing a short birdie attempt on the fifth to build some momentum.
Tanihara barely gave his opponent a look-in from that point on, leaving the pressure on McIlroy and Spieth in their next outings to keep their hopes of success alive.