World number two Serena Williams is out of the ASB Classic after unforced errors cost her dearly in her second round match against fellow American Madison Brengle.
The first seed showed signs of struggle early on in the contest as she set up winners throughout but was unable to capitalise with final shots.
Brengle then broke service in the first set when the scores were tied 4-4 - she went on to win the set on her service 6-4.
The 25-year-old pushed Williams all around the court - a strategy which drained the 22-time grand slam champion both physically and mentally.
Brengle then broke service once more in the second set at 3-3 but allowed Williams back in immediately after and even risked losing the second set on three separate occasions, but once again Williams failed to capitalise on set points.
The second set eventually headed to a tiebreaker which Williams finally claimed 7-6(3).
The two Americans then traded blows in the third and final set, neither giving away service with the scores sitting at 4-4.
Then, with the match sitting at 5-4 to Brengle, the world number 72 found herself with two match points but was unable to convert as Williams displayed pedigree spirit to remain in the contest.
The set reaching deuce, Brengle took advantage for another match point before Williams gave away the match with a double fault.
After winning the match 6-4, 6-7, 6-4, Brengle said she was in disbelief as she giggled through her on-court interview.
Williams recorded 88 unforced errors during the match compared with Brengle's 30.
Williams quickly departed the court after the match.