By Jon Wertheim The field is wide open at the first slam of the year. Consider the recent Australian Open women’s singles champs: 2022: Ash Barty (retired) 2021/2019: Naomi Osaka (pregnancy absence) 2020: Sofia Kenin: Ranked No. 143 2018: Caroline Wozniacki (retired) 2017/15: Serena Williams (retired) 2016:Angie Kerber (pregnancy absence) 2014: Li Na (retired) It’s hard to recall a time when there were only two former champions (Victoria Azarenka—a decade ago; and Kenin with a triple-digit ranking…and tennis being tennis, they play each in round one) in the main draw of a major and neither w…