A bitterly disappointed Jack Sock was forced to concede the ASB Classic to eighth seed Roberto Bautista Agut after succumbing to flu symptoms in the second set of Saturday's final.
Sock battled illness in the semi-finals, but the unseeded American was unable to carry on 24 hours later as he retired when trailing 6-1 1-0 in Auckland.
The world number 26, who stunned four-time champion David Ferrer and Kevin Anderson en route to the decider, was visibly ill from the first point of the match and looked dejected with his head slumped his hands when trailing 5-0 at the change of ends.
Though lifeless and out of sorts, Sock somehow managed to snap Agut's run of five consecutive games after rallying from 0-30 down to finally get on the board.
Sock sent a forehand wide in the very next game as Agut closed out the set and at the end of the stanza - surrounded by medics - the former could be heard saying: "I'm having an out-of-body experience. I don't feel like I'm here."
But Sock stepped out for the second set, albeit for one game, before pulling the pin ahead of the Australian Open, which gets underway on Monday, handing Agut his fifth ATP Tour title.
"I'm sorry to the fans. I wanted to come out and at least attempt," Sock said afterwards.
Sock will face a qualifier in the first round at Melbourne Park next week, while Agut opens against Martin Klizan.