The 25-year old Argentine centre-back, who joined on loan last month, made his first appearance for the Black Cats when coming on inside the first quarter-hour of the 2-0 home loss to Hull City.
Manager Gus Poyet was forced to do a reshuffle when Wes Brown was sent off in the fourth minute, sending on Vergini for striker Fabio Borini, and he is likely to be on the pitch from the start at the Etihad Stadium on Wednesday.
"I don't think Santiago expected to play last weekend, but inside the opening 15 minutes he was on the pitch. It's vital to be ready to show your quality," Poyet said.
"It's always good to have options just in case. That's why I need the whole team to be ready."
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