The 33-year-old midfielder played the full 90 minutes of the Black Cats’ 0-0 semi-final second leg draw with Portsmouth on Thursday evening after his mother, Susan, lost her battle with cancer on Wednesday.
He spoke of his anguish in an Instagram post on Friday morning as he thanked fans for their condolences.
Leadbitter wrote: “Last couple of days have been tough, not just myself but my 2 sisters too. To lose my mam on Wednesday was horrible, but I know now she is at peace now after tough battle of cancer. She now rests alongside my Dad.