The Black Cats will face stern competition in the race for promotion, with a number of their third tier rivals having already completed some eye-catching deals – which could prompt some worry. Scroll down and click through the pages to see EVERY deal completed in League One this summer so far:
13. Oxford United
In: Kevin Berkoe (Wolves), Sam Allardyce (Bury), Tariqe Fosu (Charlton Athletic)
Out: Charlie Raglan (Cheltenham), Curtis Nelson (Cardiff City) Photo: Julian Finney
14. Portsmouth
In: James Bolton (Shrewsbury), Sean Raggett (Norwich City - loan), Ryan Williams (Rotherham United), Paul Downing (Blackburn Rovers), Ellis Harrison (Ipswich Town)
Out: Adam May (Swindon Town - loan), Matt Clarke (Brighton & Hove Albion) Photo: Pete Norton
15. Rotherham United
In: Shaun MacDonald (Wigan), Daniel Barlaser (Newcastle United), Julien Lamy (Plabennec), Freddie Ladapo (Plymouth Argyle)
Out: Joe Newell (Hibernian), Dominic Ball (QPR), Ben Purrington (Charlton Athletic), Darren Potter (Tranmere Rovers), Will Vaulks (Cardiff City), Ryan WIlliams (Portsmouth), Jerry Yates (Swindon Town - loan) Photo: George Wood
16. Shrewsbury Town
In: Ethan Ebanks-Landell (Wolves), Daniel Udoh (AFC Telford), Joe Murphy (Bury), Ryan Giles (Wolves - loan), Aaron Pierre (Northampton Town), Steve Morison (Millwall - loan)
Out: Steve Arnold (Northampton Town), James Bolton (Portsmouth), Lee Angol (Leyton Orient), Aaron Amadi-Holloway (Brisbane Roar) Photo: Pete Norton