Paolo Di Canio has slated his Sunderland team following their 3-1 defeat to newly-promoted Crystal Palace on Saturday.
The Italian branded his strikers "empty in the brain" after their performance at Selhurst Park, with South Korean Ji Dong-Won bearing the brunt of his criticism following a missed near-post header in the first half that resulted in him being substituted.
And despite bringing in 11 new signings this summer, the Italian claims his side still need more players with "heart."
"I cannot change the heart of my players," the Italian told reporters. "One time we did a delivery very well and Ji didn’t push his head forward."
"I am more disappointed than him [about him being substituted]. I think also the fans [were] because the expectation on him is very high because he can do much better, even in only keeping the ball.
Di Canio also criticised youngster Connor Wickham and captain John O'Shea, reprimanding his skipper for the challenge that saw him sent off on 77 minutes for conceding a penalty.
"We don’t ask the moon: do not lose every ball under pressure. The young fellow [Wickham], he can keep the ball much better if they have more desire; and if they play less empty in the brain they can keep the ball much better.
"At this moment they are empty. Our leader [O'Shea] didn’t react in the way he should. That is terrible, because it was a crucial game for us. It’s absolutely poor and not acceptable.
"Now everybody can understand why we asked for a few players [this summer]."
Sunderland have gone seven games without a win in the Premier League and the north-east side face Arsenal, Liverpool and Manchester United in the coming weeks, which could see them still stuck on one point.
But Di Canio says he is not preparing for the wors: "If I think about this, it is better that I retire from being a manager," he said. "We have the ability and quality to beat any side."