The Black Cats are eager to improve the competition for places at the Stadium of Light.
Dick Advocaat has revealed that he is looking to add as many as four new signings to the Sunderland squad ahead of the close of the transfer window, as he seeks to ensure the club are not battling relegation again next season.
ESPN have quoted the Dutchman as responding to a question on the number of new faces he is looking at with: "Three, maybe four (new players).
"It is still very quiet on the transfer market, in England as well. It's strange. But we still hope that we can get three extra players in the squad. That makes everything a little bit easier.
"What I have said already, and we discussed it with Lee and with the president at the end of last season, we need more competition in the squad."
The 67-year-old appeared happy with the two defensive signings he has made, with Sebastien Coates joining from Liverpool after a loan spell and Adam Matthews arriving from Celtic, but made it clear that the club have to strike the right chord between value for money and quality when it comes to improving the Black Cats squad.
"We now have two with Coates and Matthews, but hopefully we will still try to get some other ones in as well," Advocaat added.
"Everybody thinks abroad that England is the country of the money, so we have to be very careful with the money, we have to bring the right players in who can compete with the other players.''
The former Rangers boss took charge of Sunderland in the middle of March, and went on a decent spell of form that ensured they were spared having to save themselves on the last day of the season.
A man of his experience will be well aware of the quality needed at top clubs, with Sunderland said to be looking at the likes of Netherlands international Jeremie Lens this week according to the Mail, a player that would certainly offer something at the Stadium of Light.