Swansea City boss Garry Monk questioned his players' desire after Leicester City cruised to an impressive 3-0 win at the Liberty Stadium on Saturday.
The defeat, and the manner of it, will increase the pressure on Monk, whose side was undone by a Riyad Mahrez hat-trick for the table-topping visitors.
"We were extremely poor, especially in that first half. It's not acceptable at all," Monk told Sky Sports.
"What we're giving right now is not what it should be.
"We can debate the two goals, the first was a handball and the second was offside, but it's not about that, it's about the principles we have set as a club, as a team and we're not doing it."
The defeat leaves Swansea four points above the relegation zone after a run of one win in 11 Premier League games.
Monk added: "It's very difficult to put your finger on it. You feel you are getting somewhere - we had a really good reaction against Liverpool [last weekend] - and then we get that type of performance. It's very frustrating.
"We're going to have to find a solution very, very soon. It's important these players fight for each other because they're the only ones that can."
