At their peak, Liverpool was a team that the opposition dreaded facing. Jurgen Klopp, known for his " heavy metal" approach to football, created a side that smothered opposition in their half with extremely aggressive pressing and high intensity. "High Pressure" is a term that is constantly thrown around in modern soccer, however to pressure an opponent in their half demands more than just intensity and the willingness to run. It requires organization and everyone to be on the same page. For example, Mo Salah must be able to trust that when he presses, his midfielders are where they need to be. For years that was the case. Everyone knew their role, and the Liverpool team hunted in packs once they lost the ball, often resulting in them quickly regaining it and reestablishing their dominance in possession. Wave after Wave of high pressure often wore opponents down, causing them to fatigue and leaving them susceptible to making mistakes that Liverpool often capitalized on. For years this was the case- extremely efficient high pressing defense followed by direct forward play feeding potent forwards thirsting for goals and opportunities.
However, this is not the case this season. The pressing, once organized and everlasting, is now scrambled and ineffective. And the intensity that was a trademark of a Jurgen Klopp team is no longer. That disorganization and lack of intensity means their pressure is futile and easy to play through. The Liverpool players no longer close the distances they once did and are not moving in a coherent unit, meaning that opponents now have more time and options to break the Liverpool press.
This could be due to several reasons. It could be because of mental, emotional, and physical fatigue from playing full throttle for multiple years. Having to be on edge mentally and physically all the time comes at a cost, and this season might be evidence that the players simply cannot take themselves to that place anymore. In addition, the disappointment from the previous season might also be a factor. Coming within 15 minutes of winning the prem and a Courtois masterclass preventing them from winning the Champions League must play heavily on the minds and hearts of the Liverpool team. Whatever the reason might be, the lack of press translates to Liverpool's dip in form and increase in mistakes. Liverpool is constantly conceding goals now, and in fact, they have conceded first in the past six games away from home. And their home form is not much better, with stats having them at 40% likely to be losing at halftime. The lack of press, intensity, and compactness is why Liverpool is defensively vulnerable.