The Black Cats have already brought in defender Daniel Ballard and re-signed winger Jack Clarke, while Patrick Roberts, Bailey Wright and Lynden Gooch have all agreed new deals.
Yet it remains clear that Sunderland are short of striker options as back-up for Ross Stewart, while they are also looking to strengthen at full-back.
There is also a need to sign another goalkeeper, with Anthony Patterson the only senior option between the sticks.
Here are some of the players who have been linked with a move to the Stadium of Light this summer.
1. Nathan Broadhead - Everton
Sunderland remain interested in the Everton forward, who impressed on loan at the Stadium of Light last season, yet they may have to wait for a decision until later in the window. Broadhead has travelled with the Toffees squad for their pre-season tour of America, with Frank Lampard keen to take a closer look at the 24-year-old. Another loan move may also prove complicated as Broadhead only has a year left on his contract at Goodison Park. Photo: Frank Reid
2. Jack Rudoni - AFC Wimbledon
The attacking midfielder, 21, is someone Sunderland have been tracking for a while. The Black Cats have seen a bid rejected for Rudoni this summer, with Wimbledon valuing him close to the £1miilion mark, and he now looks set to sign for Championship rivals Huddersfield instead. Photo: Alex Davidson
3. Troy Parrott - Tottenham
A versatile forward who played through the middle and on both flanks for MK Dons last season. Parrott appears to be the type of player Sunderland are looking for to support Ross Stewart in attack, while Tottenham plan to loan the 20-year-old out for another season. Spurs will have to weigh up what is the best option for the young striker, who has travelled with the squad for their pre-season tour of South Korea. Photo: Pete Norton
4. Reda Khadra - Brighton
Following an impressive loan spell at Blackburn in the Championship last season, a number of clubs are thought to have expressed an interest in the 21-year-old winger. While Sunderland were said to be tracking Khadra, the Black Cats are prioritising other positions. Sheffield United now appear to be leading the race to sign Khadra this summer. Photo: Lewis Storey