New Tranmere boss Micky Adams has bolstered the clubs attacking options with Cardiff's Danny Johnson on a one-month loan.
Full-back Maynor Figueroa has returned to Wigan on a one-month loan deal from Hull.
The former Bolton full-back has completed a medical on Wearside and will officially join the Black Cats' squad when the winter transfer window opens.
Manager Gus Poyet said: "I can confirm Marcos is going to be with us for the rest of the season on loan from Fiorentina, which is something very important.
"I was looking for a player in that position on the left side and I hope he will help us and everybody will like him.
"I am delighted that everything is agreed."