Newcastle boss Alan Shearer hit out at Joey Barton after the midfielder was sent off for a lunging tackle on Xabi Alonso in the 3-0 defeat at Liverpool.
Playing for the first time since 28 January following an injury, Barton will now miss the rest of the season.
"I wasn't happy, I was bitterly disappointed at the way that happened," Shearer told BBC Sport.
"I asked him to stay calm in the heat of the battle but it was a stupid tackle and he deserved to be sent off."
Sunday's appearance was only the ninth time Barton, who has had a troubled career both on and off the pitch, has played for the Magpies this season.
His straight red card automatically triggers a three-match ban, ruling him out of the games against Middlesbrough, Fulham and Aston Villa as Newcastle bid to avoid relegation.
I think that the experience of this year will be fantastic
Liverpool manager Rafael Benitez
"It's about 90 minutes, not about 75 or 80 minutes," said Shearer. It's about keeping calm for 90.
"I think it would be wrong to discuss his future now but I'm not very happy."
Outclassed by title-chasing Liverpool, who as well as scoring three goals hit the woodwork three times, Newcastle remain mired in the relegation zone, three points from safety.
"I'm bitterly disappointed to have lost the game," stated Shearer. "No complaints about the way we lost it - I think the first goal was probably offside, just, but would that have changed the outcome of the game? Probably not.
Benitez hails mentality of Liverpool squad
"They were the better side and deserved to beat us. It could have been a few more but for the woodwork but we'll regroup. This game wasn't going to save our season today but the next two will."
Despite Newcastle's woeful performance, Shearer remained upbeat about the attitude of his players for the run-in to the end of the season.
"I've seen enough from the boys in training and against Portsmouth last Monday to suggest that if we play in a similar sort of way and create the chances that we did in that game, that might be enough to keep us up," added Shearer.
"But we know how important that next game against Middlesbrough is - to both clubs."
Liverpool manager Rafael Benitez was happy with his side's performance as Yossi Benayoun, Dirk Kuyt and Lucas Leiva scored the goals in a straightforward win.
Manchester United remain three points clear at the top of the Premier League with a game in hand over the Anfield outfit but Benitez believes that this season will stand his squad in good stead, win or lose.
""I think that they have difficult games to play, so we will see," said the Spaniard. "We have to keep the belief.
"I think that the experience of this year will be fantastic. If we can win it will be amazing, if we cannot we have to keep going and going and the experience for the players for the future will be really good."
Alonso was carried off following the tackle by Barton but Benitez described the ankle injury as "a knock, it will be very painful for one or two days, hopefully it will not be serious".
Star striker Fernando Torres missed the match and Benitez confirmed: "He felt something in his hamstring so we left him out just in case because we know that he has had a problem before and it was a big risk."
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