Nigel Pearson has warned his side are in for a long and difficult season if they fail to drastically improve at the back.
It was a case of De-Ja-Vu from last season as the Robins scored twice but still left Ashton Gate empty-handed as Sunderland's two strikers Ellis Simms and Ross Stewart had a field day against City's fragile backline.
The visitors took an early lead in the fourth minute when Kal Naismith was dispossessed deep in his own half by Ross Stewart. Simms picked up the ball and unleashed an effort from distance that caught Dan Bentley off guard.
