No one would call it a surprising result as Liverpool is performing better than Arsenal on the league as well. The knockout match was surely a very competitive one. Both of the team performed well but it was Liverpool who succeeded in scoring. This loss on the home grounds of Arsenal would surely be a sad one for its fans. There are some surprises on the 3rd round but on overall, we are going to see the top teams in 4th round.
Sometimes it doesn't need to be a team that controls the game to be the winner and Liverpool managed to perfectly beat Arsenal who controlled the game even though some of the players who became the foundation of Liverpool could not strengthen the team, but it didn't really affect their game.
Losing to Liverpool made Arsenal suffer three consecutive defeats in all competitions, and that's not good enough for Arteta because it will make it even more difficult for them to compete in the title race as well as in the Champions League, because it means there is a problem in terms of them maintaining consistency and Arsenal will be like last season very good at the beginning of the season but slowly they failed in many matches.