Sunderland manager Paolo Di Canio was angry at captain John O'Shea after the defender's "terrible" dismissal in his side's 3-1 defeat at Crystal Palace.
The game was level at 1-1 when the 32-year-old was sent off in the 79th minute for a professional foul on Dwight Gayle, who scored the penalty.
Stuart O'Keefe added a late third goal to leave Sunderland second bottom.
"Our leader didn't react in the way he should. That is terrible because it was a crucial game for us," said Di Canio.
"The penalty didn't come from a dangerous situation. It's absolutely poor and not acceptable.
"It was difficult to see this goal at this level. John O'Shea did something really wrong but he is an experienced footballer.
"It won't determine the outcome of our season but if we don't think every ball could be crucial, then it could be a problem."
Sunderland have now only collected one point from three Premier League matches and play Arsenal, Liverpool and Manchester United in three of their next four games.
Danny Gabbidon put Palace ahead and Steven Fletcher equalised, before two goals in the last 11 minutes gave the Eagles their first league victory of the season.
Di Canio, who has won only three of 10 games since becoming Sunderland manager at the end of March, was unhappy with his side's defending.
"It is not just with John O'Shea, but with a few players and there is not the right desire," added the Italian. "I cannot change the heart of my players.
"We were on top for most of the game but three very pathetic goals that we conceded did not give us the chance to fight back."
Sunderland have signed 12 players this summer but Di Canio hinted there could be further additions to his squad before the transfer window closes at 23:00 BST on Monday.
"Now everybody can understand why we asked for a few players in areas of the field," he said.