Di Canio was dismissed after Sunderland failed to win any of their first five games in the Premier League, with Ball placed in temporary charge.
Cuellar did not feature in Di Canio's plans but has returned to first-team action under Ball, with the Spaniard adamant that things are more positive on Wearside despite last weekend's 3-1 defeat to Liverpool.
He told The Mirror: "A difficult week? No, it was a good week because we won in the cup, everybody was happy and got back their confidence.
"There was a feeling that a family was being fractured with everything that was going on, but now it is pushing us in the right direction."
Sunderland confirmed yesterday that Ball will remain in charge of first-team affairs this week, including Saturday's clash with Manchester United at the Stadium of Light.