Boss Steve Bruce has moved quickly to ease fans' fears over next season by bidding around ?10million for Wes Brown, Darron Gibson and John O'Shea.
The three players - who are one-club men - all struggled for starts last season and could be tempted with a move away from Old Trafford for first-team football.
Wanted men: Wes Brown, John O'Shea and Darron Gibson are the subject of a bid from Sunderland
Brown has been discarded by Sir Alex Ferguson after losing the faith of his manager, while Gibson has come in for strong criticism from his own fans - who forced to close his Twitter account after a wave of abuse.
O'Shea is the one who Ferguson would most like to keep but the player may warm to the idea of a bigger role at a smaller club.
Bruce has a large transfer kitty to spend this summer after offloading Henderson to Liverpool for ?16m, while he also sold Darren Bent to Aston Villa for ?24m in January.
On the lookout: Steve Bruce is desperate to reinforce his squad
Meanwhile, Sunderland chairman Niall Quinn has moved to reassure the club's fans of its ambition as Henderson departs.
He said: 'Jordan is a credit to himself, his family and Sunderland's academy and everyone here wishes him the very best for the future. I'm pleased that we got the deal to a level that we felt was right for our club.
'We know the areas that need strengthening and the type of player we need in order to progress, and the job of bringing those players to the club is continuing at a pace.'
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Explore more:People: Alex Ferguson, Darren Bent, Wes Brown, Steve Bruce, John O'Shea, Niall Quinn Places: Liverpool