Middlesbrough head coach Aitor Karanka conceded Liverpool were "impossible to stop" as they romped to a 3-0 win at the Riverside Stadium on Wednesday.
Adam Lallana scored in each half, either side of setting up Divock Origi's fifth goal in as many games as Liverpool's victory sent them up to second place in the Premier League.
The division's top scorers, Jurgen Klopp's men became the first Liverpool side to win on Teesside since 2002, significantly stepping up their attacking threat after the break.
Having seen his charges concede three goals in a home game for the first time since August 2014, Karanka hailed the Reds as the toughest top-flight opposition he had taken on.
"It was difficult because before this game we have competed against every team we've played," the Spaniard, who introduced Grant Leadbitter and Stewart Downing before the hour mark, told the club's official website.
"But I think they were the best team we've faced this season.
"We tried, especially in the second half with two new players, to press higher. It proved impossible to stop them. I can admit they were much better than us.
"But I can't say anything bad about my players because they gave everything on the pitch.
"Now, all we think about is our important game with Swansea [on Saturday].
"We have to remember how good we've been in the games before this, against Bournemouth and Hull City."