Simona Halep

What to Watch at US Open: Williams-Halep, Konjuh-Pliskova

After Serena Williams won her third-round match at the U.S. Open, she was asked how happy she was with her performance to that stage.

Her answer: "Obviously I don't feel like I'm 'Serena' out there yet, but hopefully she'll come around the second week."

After Williams won her next match with another strong showing to reach the quarterfinals, she was asked whether she felt any differently about things. Had Serena shown up yet?

The answer this time: "Well, she's coming. She hasn't quite come out yet, though."

If she does, look out.

Heading into Wednesday's quarterfinal against No. 5 Simona Halep, Williams has been rather dominant. Not...