Kimiko Date-Krumm, the oldest singles player at the Australian Open, lost in the first round to Swiss teenager Belinda Bencic, 6-4, 4-6, 6-3.
The 43-year-old Japanese veteran started with a 3-0 lead but lost momentum as the 187th-ranked Bencic rallied back with a break and won the last four games of the first set.
Date-Krumm battled back in the next set, prompting her 16-year-old opponent to bounce her racket in frustration after one flubbed point.
Bencic took control in the third, as Date-Krumm wilted with temperatures rising.
Playing her first Australian Open main draw, Bencic won two junior Grand Slam titles last year at the French Open and Wimbledon.
This was Date-Krumm's 48th time playing a Grand Slam tournament. She was the oldest woman in the draw by a decade.