The cameras attempted to pan towards Liverpool’s dropped goalkeeper on more than one occasion here but no one was really noticing. Jürgen Klopp’s side made sure that Loris Karius was not the story on a night when Adam Lallana starred in a convincing victory and they played the kind of scintillating football that has become their trademark this season.

Simon Mignolet replaced Karius after his recent errors but the saga that dominated the build-up to this game was soon forgotten. Liverpool started steadily after dropping points in their last two games but when they hit their stride Middlesbrough were simply no match. If the hosts’ manager, Aitor Karanka, was being brutally honest a three-goal defeat was probably not the worst result.

Each goal was the result of sharp team interplay and Lallana’s fine campaign continues. He opened the scoring with a header, set up Divock Origi for the second and made the points secure with a brilliant third, as Liverpool went above Arsenal in the Premier League to second place.

Karius watched from the bench as Liverpool controlled the tempo throughout. Klopp said afterwards that the German would not be restored to the starting XI immediately and that Mignolet –who had little to do on Teesside – would keep his place for the foreseeable future.

“I’m not interested in public pressure, I’m interested in the boy and there’s no reason to push him through this situation,” said Klopp of the decision to drop Karius. “At the end they were little mistakes and they can happen. There is no reason to push him [Karius] through this situation, especially when you have a goalkeeper like Simon Mignolet.”

Asked how Karius took the news, Klopp added: “How you can imagine. It was not that he immediately wanted a hug, but it’s normal. It’s football. It’s all OK but of course for the player it was not the best moment in life. Now it’s Simon’s chance.”

Mignolet therefore started a Premier League match for the first time since mid-September. The Belgian spooned a clearance high early on but was relatively assured during a half in which Liverpool had the edge.

After a tight opening 20 minutes when the only effort on target was a 25-yard strike from Middlesbrough’s left-back, Fábio, Klopp’s side began to take control. They had pressed and dominated possession without creating too much, until a fine team move gave them the lead.

In the 29th minute Georginio Wijnaldum played a fizzing ball out right to Nathaniel Clyne, who ran on to the pass with pace and made room to cross deep. Lallana timed his run well in the penalty area and rose superbly to nod Clyne’s accurate ball past Víctor Valdés and in at the far post.

Adam Lallana heads home the opening goal of the game. Photograph: Richard Sellers/PA

It was the kind of team goal that Liverpool have become accustomed to producing this season, and the lead was one that they probably deserved. Middlesbrough almost responded immediately, Viktor Fischer forcing a smart stop from Mignolet at the near post, yet it was Liverpool who came closest to another before half-time through Sadio Mané, who struck a post after being sent through by Origi.

Middlesbrough were on the back foot immediately in the second half and Klopp praised his side’s slick attacking. He said: “It’s not the first time this season. The boys are capable of doing things like this, it is really good. The third goal, it’s perfect. It looks simple but it isn’t. It was a good game tonight. I wouldn’t have expected it but the reaction was great.”

Liverpool were well on top and Mané , in particular, was in the thick of it. In the 55th minute the away supporters appealed for handball against Calum Chambers after Mané’s shot from Roberto Firmino’s low cross, but although the ball appeared to strike an arm it was tucked into Chambers’ body.

Soon, though, those supporters were celebrating a second and once again it was a fine team move with Lallana at its heart. The midfield interplay was simply too good for Middlesbrough and by the time Wijnaldum slipped the ball through to Lallana, the red and white Boro shirts were spinning. Lallana raced to the by-line and pulled it across for Origi who finished coolly from close range.

Karanka had already tried to stem the tide by bringing on Stewart Downing and Grant Leadbitter, but his team were being comprehensively outplayed and the game was done soon enough. This time Origi was the provider and Lallana the scorer, his sixth of the season from another fine move in the 68th minute that had similarities to Liverpool’s second. Origi raced on to a loose ball and as Firmino made the decoy run to the near post, Origi pulled it back to the far instead where Lallana finished emphatically.

“We’ve lost against one of the best teams that we’ve played so far this season,” said Karanka. “When teams like them play at that level it’s difficult. We tried in the first half, in the second I tried to put two fresh players on for more high pressure but it’s difficult because of the way they move the ball.”