In her comeback tournament after a four-month struggle with shoulder and knee injuries, the 22-time grand slam winner was dumped out in the second round after hitting a staggering 88 unforced errors in a 4-6 7-6 (7-3) 4-6 loss.
The 35-year-old struggled to master the windy conditions, labeling her performance against world No. 72 Brengle as "unprofessional."
"She obviously did a much better job than I did," Williams told reporters. "I really abhorred the conditions. I don't think I've ever hit 88 errors in my career; I could Google that and that's probably accurate.
"I really think I played -- I'm trying to think of a word that's not obscene -- but that's how I played," added Williams. "You really have to go back to the drawing board, because it's quite frankly unprofessional."
Williams, who last week celebrated her engagement to Reddit co-founder Alexis Ohanian
, is bidding to win a seventh Australian Open in Melbourne later this month and break the Open era record for grand slam titles in the process.
"I felt good [after the second set], but I never got into my rhythm; I never hit any returns in the vicinity in the court. I've never returned like that in my life," she lamented.
"It's a little frustrating, especially since I worked so hard in the off-season, but at least the conditions won't be like this in Melbourne."
Making her debut appearance in Auckland, Williams became only the second top five scalp of Brengle's career after the 26-year-old beat Petra Kvitova in Germany last year.
"88 unforced errors is too much, just way too many. It's a lot. I can't expect to win hitting that many errors," Williams said.
"I couldn't get used to the wind; my opponent was playing in the same conditions, and maybe the wind was more suited for her game, but it was really annoying me for whatever reason."
Williams last won the Australian Open in 2015 and will begin her quest to become the most decorated grand slam singles champion in the Open era later this month.
A bad day for the Williams family was compounded after Venus was forced to withdraw after her first round win over Jade Lewis.