I like Stephens at -4 and Isner at +4 and on they moneyline at +271
Stephens isn't in top form but she's playing well and she always plays better at majors. Her power plays well on the hard court and Sevastova is consistent but doesn't have the same serve and power.
Isner is playing the best tennis of his career and he can match Del Potro's power, Isner doesn't play a lot of long points, he should be fine in the heat. Del Potro is playing well but he's had some wrist issues recently and hasn't been consistent
Stephens isn't in top form but she's playing well and she always plays better at majors. Her power plays well on the hard court and Sevastova is consistent but doesn't have the same serve and power.
Isner is playing the best tennis of his career and he can match Del Potro's power, Isner doesn't play a lot of long points, he should be fine in the heat. Del Potro is playing well but he's had some wrist issues recently and hasn't been consistent