Pegula was beaten 6-4 6-1 by twice-champion Victoria Azarenka (33) as the American fell at the quarter-final hurdle of a Grand Slam for the fifth time in her career.
Pegula was the highest seed left in the draw after Iga Swiatek (21) and Ons Jabeur (28) made early exits and she was a strong contender for the title in Melbourne after impressing in the American team's victorious United Cup campaign.
"I feel like I had a good chance to go deeper here than I did by losing tonight... I had some really good wins at the start of the year and this tournament," Pegula told reporters.
"I think I can walk away saying it was a successful tournament and a successful trip to Australia. I definitely felt like I was more confident going in that I could go deeper.
"I wasn't as surprised by the results of making a quarter-final or fourth round or second week. It felt more normal for me, which is a good thing."
Pegula said she struggled to get a grasp of the night conditions having played her first four matches during the day.
"The balls are slower and heavier, but at the same time every time I tried to hit out, I felt like I was missing, not by a lot, but a few inches here and there," said Pegula, who made 31 unforced errors.
"I think I started second-guessing myself with hitting out. That kind of rolls into making more mistakes than you want to."
Defeat also marked the third straight year Pegula had failed to move past the quarter-finals at Melbourne Park but she insists she has come a "long way".
"I just think I need to also take a step back and look that I made three quarter-finals in three years," she added.
"I think I can be... a perfectionist and (be) really tough on myself. Obviously I'm upset about tonight, but at the same time I'm putting myself in these positions to go deep in these tournaments. I think I've proven that.
"I've been super consistent, so just keeping a good mindset that I'm putting myself in position at all these events. Hopefully it comes together."
