Yeah so after Kerber's loss today and Ostapenko's loss tonight, Sloane and Serena are the only slam winners from the last two years. Actually they're the only two slam winners since 2014 (Sharapova at 2014 French) left in the draw. Now, that's mostly because Serena won 3 of 4 in 2015 (Panetta won the US Open). Kvitova won the 2014 Wimbledon, but she lost today too. Li Na won the 2014 AO. So your defending champion and Serena are the only two recent slam winners in the draw and Maria Sharapova is the only other slam winner still left in the draw.
Of course, you do have Keys, last year's finalist and Pliskova 2016s finalist against Kerber. So this has turned into a group of people who do well at the US Open basically. Kanepi a quarterfinalist here last year (and 2010). Sevastova a quarterfinalist here last year (l. Stephens in third set tiebreak). Cibulkova an AO finalist. Svitolina the only top 8 seed left besides Sloane and Pliskova. And then Osaka, winner of IW. Sabalenka winner of New Haven right before the US Open. Riding a serious hot streak. Really coming into her own basically. Starting back before Wimbledon making the final of Eastbourne (l. Wozniacki). Looking at her match activity this year is funny. Because she lost to Barty in the first round of the AO. Barty still in it here. Lost to Tsurenko before that in the quarterfinals of Hobart. Lost to Tsurenko's upcoming opponent Vondrousova in the third round of IW. Then beat Vondrousova in the first round of 'S-Hertogenbosch, AFTER losing the first set to love. Could play Vondrousova if she beats Osaka. Lost to Mertens in the final of Lugano on clay and then again in Canada a few weeks ago. Mertens still in it here. And I worry is a serious threat to Sloane. Though I expect Sloane to figure it out after her recent loss to her in Cincy. Just sort of strange that with everyone that has fallen, of those that remain, Sabalenka has played most of them this year. But, of course, one of those people is not Osaka. Has not played Osaka this year. They've never played in fact. Sabalenka perhaps, somehow, more powerful than Osaka. But the beat down Osaka put on Sasnovich today should send a message, even if she wasn't beating Kvitova. Should be an awesome match. The only person left I haven't mentioned is Suarez Navarro. Sabalenka beat her in the New Haven final last week. So clearly playing well right now as well. Sharapova has won 4 of their 5 meetings. They've never played in a slam.
Also, I don't know if anyone picked this out when the draw first came out. But I just got curious tonight. Serena would have been the 25th seed if left at her ranking of 26 because Buzarnescu is out. Gavrilova was seeded 25th with Serena at 17. Gavrilova is in Sloane's 16th. Would have had to play Vika in the second round. And Sloane in the third round if she'd beaten Vika. Bad for Vika. Sloane. But also perhaps for Serena. All got lucky she got moved about. Of course, Venus was not so lucky.