Kasatkina 1.79, Mertens 2.24
Kasatkina won their only previous meeting. That was in the Daytona Beach ITF tournament in January 2015. She won in 3 sets on clay.
This season Mertens has better overall results and stats. On hard courts she is also ahead. She has come through the qualifying rounds this week and beat Bertens in 3 sets in the main draw. She has won 71% of her hard court matches this season. Her stats are boosted by her winning the title in Hobart in January as a qualifier.
Kasatkina played well to beat Strycova in 2 sets in the last round. Strycova had a 3-0 lead in the opening set but then lost her serve 5 times in a row. She won the title in Charleston, USA on clay in April but apart from that she has had a poor season.
Value on Mertens as underdog. Three sets seem likely. Lay Kasatkina below 1.50
Update: Mertens won in straight sets.