Jurgen Klopp blamed his players for becoming embroiled in a fight at Swansea City as they lost their unbeaten 18-match run to the Premier League's bottom club.
Liverpool failed to grab a late draw to extend their lead over fifth-placed Tottenham Hotspur as they lost to a single goal from Alfie Mawson - and Klopp himself clashed verbally with a home supporter.
It was Liverpool's first defeat since October, but the points were priceless for Swansea, who cut the gap between themselves and those above the relegation places to just three points.
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"I am more frustrated about the performance than the result," he said. "We were just not good enough, especially in the first half. We didn't play how we wanted to play.
"We didn't keep the right positions we needed to, to cause them problems and didn't stretch them. We gave them the opportunity to score and then we did exactly what Swansea wanted.
"They didn't need to play, they needed to fight and we did exactly what they wanted and their confidence grew."
Liverpool missed plenty of opportunities from their normally clinical strikers Sadio Mane, Mo Salah and Roberto Firmino.
They also came up against a goalkeeper at the top of his game in Swansea's Polish No 1 Lukasz Fabianski.
The only goal came against the run of play in the 41st minute when Mawson swept the ball in at corner and Virgil van Dijk had misplaced a header as he tried to clear.
It summed up an awkward league debut for Van Dijk, who had previously only played in one FA Cup tie since his record £75 million (Dh385m) move from Southampton.
The frustrations provoked Klopp into his argument with a Swansea supporter around the hour mark.
"He was shouting at me all the time but I reacted. I am a human being, not just a professional manager," the German said.
"I am sure I am not the first manager who has a problem. He probably has a season ticket."
For new Swansea manager Carlos Carvalhal, this was a tactical triumph as he used a five-man defence to deny Liverpool space and then hit them on the break.
The Portuguese borrowed motor racing analogies as he left Liverpool on the hard shoulder.
"I talked with my players and said this (Liverpool) is a really strong team," Carvalhal said.
"They are like a Formula One car. But at 4pm in London it will be difficult to speed, they would be a car like any other.
"We needed to make sure there was traffic, we could not let them have open roads to drive in."
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