The Uruguayan has overseen a revival since succeeding Paolo Di Canio at the Stadium of Light, but feels the Black Cats must tighten up to survive in the top flight
The 45-year-old, who replaced Paolo Di Canio at the Stadium of Light last month, has seen Sunderland win three of his five games in charge, including Premier League successes over bitter rivals Newcastle United and title contenders Manchester City.
Their 2-1 victory over Newcastle on October 27 marked their first top-flight win of the season and they inflicted a 1-0 home win over City for the fourth campaign in a row last Sunday.
However, former Brighton boss Poyet is keen for defensive improvements as they strive to strive to stay in the Premier League and improve on last season's 17th-placed finish.
"To win the quantity of games we want to win this season, I think that defence is the key to it," he told the Sunderland Echo.
"Some people might say conceding a goal a game is OK - especially in comparison to many how we have done per game previously. They may even be right.
"But personally I think it is too many. I want to and I need to, see more clean sheets from the team."