This follows a near-identical thought process as the play on Diyas vs Siegemund yesterday that was cancelled due to the withdrawal of Diyas. You can find a link to that preview here.
Siegemund ended up facing Monica Niculescu, and struggled early. As predicted with a number of Siegemund matches, she got better as the match rolled on, winning 7-5 6-4.
Destanee Aiava scraped over the line yesterday against Paquet, and did look as though she started to fade late in the match. This is a perfect situation where I would rather take Aiava over the smaller sample size and oppose Siegemund over the small sample size of the first set, so this seems the right play for 1 unit.
1 unit Aiava 1st set winner vs Siegemund at $3.40 (+240) at Bet365