Dusan Tadic has admitted that Southampton were always confident that they would eventually break down Sunderland as they recorded a 1-0 win at the Stadium of Light.
Several saves from Black Cats keeper Costel Pantilimon kept the Saints at bay, while Sebastian Coates also made a goalline clearance.
However, Ronald Koeman's men were handed the chance to score from the spot when Ryan Bertrand was brought down by Yann M'Vila. Tadic took the penalty and buried his effort into the net to earn his side the three points.
Tadic told the club's official website: "I think when you play like this and when you have good ball possession and when you attack all the time, when your rest of defence is really good, I think it just is [a matter of] time when you're going to score a goal.
"I think we were a danger and we should have scored before. I think we were more consistent and we were all 90 minutes pushing and knocking on the door. We really want to win and to score goals, and we always need to play like that."
Southampton are seventh in the Premier League following their win over the Black Cats.