Sunderland boss Paolo Di Canio has admitted that his summer transfer activity was needed to end bad habits previously embedded in the club.
The Black Cats have signed nine players including Jozy Altidore and Emanuele Giaccherini, while players such as Danny Graham and Simon Mignolet have left the club.
Di Canio told the Sunderland Echo"Yes, it was necessary. We knew before that we were going to make a revolution.
"Obviously, the numbers were as important as the quality. You have to work so hard to understand English football because sometimes on the training sessions, it was soft and not professional.
"Their habits in the past were not good. But some of them have proved already that we were right to sign them. We have to prove it in a proper game, but I'm sure they will make a big impact in this league."
Sunderland open their Premier League campaign on August 17 against Fulham.
