Osoro and Sainz advance to their first semi-finals as a couple, dispatching the Argentinian's former partner Iglesias in straight sets at the Universidad Católica on Friday.
The five-seed suffered quarter-final exits in both Abu Dhabi and La Rioja, but will continue to fight for the BTG Pactual Chile Padel Open title on Saturday.
Looking ahead, Sainz has not made a final since the 2021 season, while Osoro's only final appearance of her career came back in September.
Watch the highlights in the video below!