Chile picked up a 1-1 draw on the road at Palestino on Friday, opening the scoring in the 64th minute via an Isaac Diaz penalty.
Sergio Lopez drew Palestino level three minutes later, to give them hope of overhauling their opponents on the away leg on Monday.
Deportes Iquique fought back from a two-goal deficit to earn a 2-2 draw at home to Catolica, with the latter - the losing finalists in the Apertura Championship decider - still taking the upper hand to the return leg.
Ramiro Costa and Jose Munoz scored inside the opening half-hour for the visitors, but Rodrigo Diaz pulled a goal back for Iquique on the stroke of half-time.
Rafael Caroca equalised two minutes after the interval, but the hosts could not find the all-important winner leaving Catolica ahead on away goals ahead of Monday's second leg.
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