Southampton manager Ronald Koeman was furious with the way his side conceded soft goals during Saturday's 2-0 loss at home to Tottenham.
And Koeman thinks his side need to show a stronger mentality if they are to halt an alarmingly poor run of form.
The Saints are still 12th in the Premier League table but they have not won any of their last six games.
They faded after a decent start at home to Spurs, conceding a 40th-minute opener when Harry Kane powered through a series of challenges and then falling two behind moments later when Dele Alli was given plenty of time to convert a Kyle Walker cross.
"I am very disappointed," said Koeman. "I think, if you watch back, the first goal of Kane, it is incredible how we, defensive-wise, play so naively at that situation.
"Three defenders against one attacker and still the attacker got a chance one-against-one with the goalkeeper.
"That was the difference today. They had more killing mentality than we showed, defence-wise and attack-wise.
"They were more clinical, showed more quality, and you can't win if you make those kinds of mistakes."
Koeman wants to see a different Southampton side when they play host to Arsenal on Boxing Day.
"We started well and were the better team on the pitch," he said. "Again we did incredible mistakes and we don't show enough killing mentality.
"We have to understand, the whole team, everyone at the club, that we are in a difficult situation at the moment.
"We know we can play good football but we need to change our mentality. This position, this situation in the table, you need something different to good football.
"You need to win every battle on the pitch and we are losing too many battles. Look, for example at the first goal.
"Maybe still the players [are] living with what they did last season. If we don't give more than 100 per cent, we have a normal team.
"We are too nice on the pitch. I don't ask for stupid falls, I don't ask for yellow, red cards, but the mentality as a player that, 'I win my battle against my opponent'."