A first-half brace from Marcus Rashford was enough to consign the Reds to their first loss since the end of January, with Eric Bailly’s own goal a mere consolation.
Klopp will now look for an immediate response in next Saturday’s home clash with Watford, and he could make changes following some poor performances at Old Trafford.
But who bore the brunt of criticism from journalists and supporters, as well as on a statistical level?
It is no surprise to see Trent Alexander Arnold (4.4) and Dejan Lovren (4.5) rated the lowest of Klopp’s side, given their involvement in both of Rashford’s goals.
Lovren’s failure to deal with Romelu Lukaku in the air and Alexander-Arnold’s failure to deal with Rashford on the ground gave United their ideal route to victory.
Interestingly, Alex Oxlade-Chamberlain (5) is not far ahead, as despite enduring a quiet first half the England midfielder did grow into the game before being questionably replaced on 62 minutes.
Oxlade-Chamberlain, Alexander-Arnold and Lovren all received ratings of three out of 10 or lower from at least one publication, as did Mohamed Salah (5.2).
Salah was brought on in the closing stages of the midweek draw with Porto, and this brief jaunt seemingly stalled his momentum, as he was decidedly muted in Manchester.
Reflecting a modest performance that included a spirited second-half fightback, Virgil van Dijk (5.7), Emre Can (5.7), James Milner (5.7), Sadio Mane (5.8) and Loris Karius (6) were all rated relatively highly.
Firmino’s cause was aided by his impressive statistical rating of 7.42, with the Brazilian making the joint-most dribbles (four), the joint-most tackles (four) and the joint-most shots on goal (three) of any Liverpool player.
Surprisingly, WhoScored’s evaluation saw Lovren deemed the fourth-best player in Klopp’s starting lineup, and the best of his back four, with 6.91.
Alexander-Arnold was less fortunate, rated at a lowly 5.84, the second-worst behind Karius, and the 19-year-old will be hoping for another start against Watford in order to address his poor display.