Liverpool's top-quality attacking force and Brendan Rodgers' preference for going out to win every game has led rather excitingly to the Reds looking to take victory simply by scoring more goals than the opposition at times this season.
With concerns lingering over the fitness and fortunes of several defenders, this attack-first, then-attack-again policy has been one mixed of both necessity and playing to the team's strengths.
Martin Skrtel, after starting the season out of the team, has been the only consistent member of the back four, with injuries and availability influencing the selections of his defensive partners.
With a summer of uncertainty ahead surrounding several Liverpool defenders and most coming back to full fitness, now is an ideal opportunity to see exactly which of the four have been performing well enough to rely on.
While we look individually at Daniel Agger, Mamadou Sakho, Martin Skrtel and Kolo Toure here, an outlook on the entire defensive aspect of the team is also required for further balance and context—check out Daniel Rhodes' work on LiverpoolFC.com here.
However, Rodgers asks his defenders to perform in a particular way within the team framework, so it's also important to see which of them plays consistently better than others.
The Slovakian has featured in 24 league appearances in a row for Liverpool, partnering all three of the others along the way. His form hasn't wavered too much this term, largely producing strong performances with some of his usual deficiencies thrown in—that's the type of defender he is.
However, he has added a few facets to his game such as far greater communication and organising this season along with the odd marauding run forward.
Skrtel is, at this point, Liverpool's first-choice right-sided centre-back and will probably remain in place until the end of the season.
Sakho or Agger?
For many, the left-centre spot is the interesting one: Should Liverpool play vice-captain and long-serving Dane Daniel Agger or £18 million new signing Mamadou Sakho? Both have tremendous assets in their game, both have admirers and those who remain unconvinced among the fanbase.
Sakho excels at stopping attacks before they really turn dangerous, nipping in to steal the ball after reading the buildup to perfection; he also has reliable and accurate passing out of defence.
Agger has struggled once more with injuries this season, giving him a stop-start campaign, but is among the best around at playing into midfield, making important tackles and in his leadership—when fit and on form. Unfortunately, that form has been all too rarely seen over the past few seasons.
At the beginning of the season, Toure put in a handful of performances which quickly made a mockery of his free transfer status, his supposed fourth-pick status out of the quartet and gave cause for some to quickly label him a potential cult hero of the Kop.
After falling out of the first-team picture entirely, he recently came back into the side at left centre-back (opposite to where he had started the season) and has performed, excepting the derby against Everton, like a player whose time at the top is up.
His swing in fortunes is alarming and has cost goals against West Brom and Fulham in particular.
Comparison and Key Metrics
Ask fans in general which defender is best at particular defensive traits and they'd probably assign heading to Sakho, perhaps tackling to Skrtel and passing to Agger. Though the centre-backs might well have those skill sets in their lockers, the tale of the season statistically shows a different story.
The stats shown are interceptions per 90 minutes on the field in the top row, clearances per 90 underneath, aerial duels win percentage third and pass completion percentage in the bottom row.
Agger, better in the air than—included for comparison's sake as this season's top-rated centre-back—Arsenal's Per Mertesacker?!
It's not something which would spring to mind for many viewers, but that's been the case. Though he has played half the games of the more regularly appearing defenders, Agger has been solid in his aerial battles this term.
Martin Skrtel has been one of the busiest in the league for consistently making clearances and interceptions, and Sakho's excellent passing and aggressive reading of the game is noted in his high scores for both interceptions and pass success.
It is Toure who yields lower than his team-mates in all key areas. This isn't to say he doesn't have a role to play over the course of the season, but he's unlikely to become established at the club at this point and is a likely candidate to depart (or be replaced as fourth-choice by a younger team-mate such as Andre Wisdom or Tiago Ilori) in the summer.
The question for Rodgers will be whether he can partner Sakho and Agger together or not at any point; after all Liverpool's injuries and defensive permutations this season, that is the one partnership which remains untested.
If not, a right-sided centre-back who can dominant better aerially than Skrtel but without losing his passing ability and reliability in fitness and consistently producing good (if not often great) form is a probable cause for upgrade in summer.
After that, it's just the simple matter of both full-back areas which need attending to...
Statistics from Squawka.com