After Northern Irish right-back Trai Hume signed a four-and-a-half-year deal with the Black Cats, bringing in another striker is now the priority for head coach Lee Johnson.
Sunderland are also short of options in central midfield and are in the market for another playmaker.
An additional centre-back may also be needed if Frederik Alves, as expected, returns to parent club West Ham.
We have taken a closer look at some of the players Sunderland have been linked with this month and the chances of them moving to Wearside:
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1. Patrick Roberts (Manchester City)
Roberts will be out of contract at Manchester City in the summer and is expected to be recalled from a loan spell at French side Troyes. It’s understood the 24-year-old is one of several attacking midfielders on Sunderland’s radar, though a loan or permanent move would have complications. Photo: Getty Images
2. Daniel Jebbison (Sheffield United)
Sunderland were in talks with the Sheffield United striker in the summer, before they signed Nathan Broadhead and Jebbison subsequently moved to Burton on loan. Jebbison has been rotated in and out of the Burton team but could be handed a more prominent role if the Brewers sell Kane Hemmings this month. Photo: Getty Images
3. Macauley Bonne (QPR)
It was claimed that both Sunderland and Wigan were monitoring the 24-year-old striker, who has impressed on loan at Ipswich this season. Yet, while Sunderland are in the market for a striker, a move to the Stadium of Light seems unlikely. Bonne is an Ipswich fan and has expressed his desire to stay at Portman Road for the remainder of the campaign. Photo: Getty Images
4. Freddie Ladapo (Rotherham)
Another striker who has been linked with the Black Cats. Ladapo has handed in a transfer request at Rotherham, yet Millers boss Paul Warne has recently said there have been no offers. The 28-year-old will be out of contract in the summer, though Rotherham do have a one-year extension so won't sell on the cheap - especially to a promotion rival. Photo: Julian Finney