Liverpool started the game brightly with Origi being denied by Sergio Rico after being played through on goal, although Sevilla should have gone ahead moments later as Diego Carlos sent a free header over the crossbar.
The chances continued to come thick and fast with Luuk de Jong volleying wide from the penalty spot, before the Dutchman was superbly kept out by Liverpool's stand-in goalkeeper Andy Lonergan after being played through on goal.
Lucas Ocampos was the next player to try his luck, fizzing a shot from distance just wide of the far post, and it was a further reminder to Liverpool that they needed to regain their concentration.
De Jong failed to net yet again, this time with a free header from a right-wing cross, but an equal talking point was the physicality of Sevilla, who were treating the game as anything but a pre-season friendly.
However, they eventually let their football do the talking by taking the lead in the 37th minute as Nolito found the top corner of Lonergan's net with a brilliant first-time finish from 14 yards.
Liverpool had been largely second best but they got themselves back on level terms just before the break through Origi, who was on hand to fire home at the back post after Nat Phillips had got a flick on from a corner.
Both teams took their time to create anything of note after the restart, although Simon Mignolet had to be alert to keep out Munir El Haddadi's first-time strike from 15 yards shortly before the hour mark.
However, tension once again boiled over with 14 minutes left, and Gnagnon was deservedly handed a straight red card for a vicious late tackle on 17-year Larouci.
The youngster had to be withdrawn - resulting in a chance for Bobby Duncan - but despite being reduced to 10 men, Sevilla found a winning goal in the final minute as Pozo found the back of the net after poor marking from the Liverpool backline.
SEVILLA (4-3-3): Rico (Vaclik 46'); Navas (Corchia 46'), Carrico (Kounde 46'), Diego Carlos (Kounde 46'), Reguilon (Escudero 46'); Fernando (Torres 46'), Banega (Vazquez 46'), Jordan (Gnangon 46'); Ocampos (Ben Yeddar 46'), De Jong (Dabbur 46', Pozo 82'), Nolito (Munir 46')
LIVERPOOL (4-3-3): Lonergan (Mignolet 46'); Alexander-Arnold (Gomez 46'), Phillips (Hoever 46'), Van Dijk (Lovren 46'), Robertson (Larouci 46, Duncan 80'); Wijnaldum (Fabinho 46'), Henderson (Miler 46'), Oxlade-Chamberlain (Jones 46'); Woodburn (Kent 46'), Wilson (Lewis 46'), Origi (Brewster 46')