The Black Cats' manager played his strongest team when the sides drew 2-2 at the Reebok Stadium, and his decision was in light of the 40th anniversary of Sunderland's last FA Cup triumph in 1973. He vows to do the same again in the replay, despite the fact they sit just six points clear of safety in the Premier League.
"When I heard that we were taking 5,000 fans down to Bolton, I don’t think it would have gone down well if I had fielded a weakened side or included a couple of very young lads, " he told The Mirror.
"The competition is so important to us and we want to try and stay in it. Also, while it’s not the main reason by any stretch of the imagination, it is 40 years since the club had that magnificent cup run and lifted the trophy, so we have to pay that some respect."
|50/1||Sunderland are 50/1 with William Hill to win this season's FA Cup|
"The busy Christmas period has taken its toll even on those clubs that carry big squads," he continued.
"But even if I had had more players, I wouldn’t have done it because this is the FA Cup and it is an important competition."
Sunderland face Wigan and Reading in their next two Premier League fixtures, with both those sides below the Black Cats in the table, and O'Neill's men will be looking to pick up points in those games to keep themselves clear of the drop zone.