Tennis star Serena Williams suffered a crushing defeat in her fourth-round loss at the Australian Open on Monday.

Williams committed seven double-faults, including four in one game; 37 unforced errors, and had a first-serve percentage of just over 50 percent that had her convinced "maybe I should have started serving lefty."

A sore left ankle may have also been a factor in Williams' 6-2, 6-3 loss to Russia's Ekaterina Makarova in the year's first major. 

The 30-year-old has played 43 singles matches at Melbourne Park since she won the first of her five Australian Open titles in 2003. Of her 54 appearances in the park since 1998, she has only lost seven; this is Williams' earliest elimination there since 2006

"I'm not physically 100 percent, so I can't be so angry at myself, even though I'm very unhappy," Williams said. "I know that I can play a hundred times better than I did this whole tournament."