Martinez took just 14 minutes to give the Argentine side the lead on Tuesday as he darted past Cruzeiro's defence to meet a Neri Cardozo set piece with a deft volley, reports Xinhua news agency.
Uruguayan midfielder Giorgian De Arrascaeta equalized with a header before Martinez scored again with a low shot after a scramble.
The 20-year-old netted his third goal just after the hour mark with an expertly placed header, but Cruzeiro reduced the deficit again via a long-range Robinho Signorini free kick.
The hosts put the result beyond doubt when goalkeeper Rafael somehow failed to keep out an Augusto Solari shot from a tight angle.
In Santiago, a second-half strike from Vladimir Hernandez gave Colombia's Atletico Nacional a 1-0 victory over Chilean giants Colo-Colo.
Hernandez drilled a shot past Augustin Orion after a slick Jorman Campuzano through ball at Colo-Colo's Estadio Monumental.
Nacional are aiming to win South America's top club trophy for a third time while Colo-Colo are vying for a second title.
In other matches on Tuesday, Paraguay's Cerro Porteno won 2-0 at Venezuela's Monagas SC and Gremio drew 1-1 at Uruguay's Defensor Sporting Club.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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