The pair were stretchered off in separate incidents at the Stadium of Light during the Premier League encounter.
However, the club has refused to put a timescale on how long it will take the duo to return to action.
"Saints can confirm that Dejan Lovren and Gaston Ramirez both suffered ankle ligament injuries during Saturday's 2-2 draw with Sunderland at the Stadium of Light," read a statement on the side's official website.
"The players' injuries are still being assessed by the medical team, so we are reluctant to place a timescale on when the duo will be able to return to action."
Southampton continue their season on Saturday when they host Yeovil Town in the fourth round of the FA Cup.