The Spanish world number 19 was leading 6-1 3-1 when Victoria Azarenka retired due to a leg injury in Sunday's Monterrey decider.
Spanish second seed Garbiñe Muguruza claimed back-to-back Monterrey Open titles as Victoria Azarenka succumbed to injury in the final.
Muguruza won the opening set and was in control of the second before former world number one Azarenka retired due to a leg injury, the score 6-1 3-1 at the time.
The victory handed Muguruza her maiden trophy of the season and seventh of her career, while it marked the first time she has defended a title.
Two-time grand slam champion Azarenka was making her first appearance in a WTA decider since returning to the Tour following the birth of her son in December 2016.
Not since March 2016 had Azarenka – plagued by off-court and fitness issues – featured in a singles final and it did not go according to plan on Sunday.
The first-set scoreline was lopsided but Azarenka was not without her chances, having squandered a 0-40 opportunity on Muguruza's serve in the fourth game.
Azarenka – the fifth seed – wasted another three break points as Muguruza held for a commanding 5-1 lead before closing out the set.
The end was in sight early in the second set after Azarenka received treatment during a medical timeout – the Belarusian eventually calling time on her title tilt following 66 minutes of play.