It's been spoken about for a while now - since January in fact - that Richardson had a desire to move back to his native London as he enters the final years of his career, and with only this season left on his contract the club were faced with little choice if we wanted a fee for him.
Martin O'Neill admitted the club had accepted a bid from Fulham after the game with Morecambe after the player was left out of the matchday squad entirely.
Speaking about Richardson's desire to leave a few weeks ago, O'Neill admitted;
Kieran came to see me a while ago in the last transfer window. For family issues and things, he thought there maybe needed a change.
It will be a shame to see Richardson go, but credit to him for not kicking up a fuss about wanting to leave way back when he originally spoke to O'Neill. He could have quite easily thrown his toys out the pram and demanded a move, as so many other 'professionals' in the game do.
It's this sort of professionalism which will make sure he's well remembered by Sunderland fans. Richardson struggled to find a regular role in the side, but did predominantly fill the role of left-back, and he did so very well. Whether he was in the middle, just off the striker or in the defence there were never any (public) grumbles, and he always performed to a high standard.
Oh, there was also the small matter of THAT freekick against Newcastle which cemented his place in Sunderland folklore for the rest of his days.
Attention turns to who will replace Richardson in the side, with it strongly suggested Tottenham Hotspur utility man Danny Rose will be joining the club after Ivan Strinic's move appears to have fallen through following injury to his back up at Dnipro.
We'll wish Kieran well at Fulham, and be sure to give him a good round of applause when we next face the Cottagers.