H2H: Halep 3 - 1 Mertens Clay H2H: Halep 2 - 0 Mertens Finals H2H: Halep 0 - 1 Mertens WTA Finals Record: Halep: 20 W / 17 L Mertens: 5 W / 1 L Who wins? My vote goes to Mertens scraping through a three set mess.