Phil McNulty, BBC Sport Chief Football Writer
A goal down. A man down. Liverpool very much second best until the introduction of substitute Darwin Nunez with 13 minutes left. Cue two goals and a stunning 2-1 win.
Liverpool were struggling for so much of the game but when it mattered the often erratic Uruguayan Nunez made the difference.
It was a big statement for Liverpool, who not only showed the character that was missing so often last season but also delivered a blow to a side who will be expected to fight them for the top four places this season.
Liverpool also did it after falling behind to Anthony Gordon’s goal and after Virgil van Dijk’s red card, which only added to the significance.
This was a huge result for Klopp and Liverpool, not merely because of the scoreline but because of the manner in which it was achieved.