It is telling that Arsene Wenger put Per Mertesacker straight back into the team against Everton immediately after the German returned from suspension.
Captain Thomas Vermaelen was fit and did nothing wrong in Arsenal's previous game against Norwich but was forced to yield to Mertesacker.
Wenger obviously values Mertesacker's presence in the center of defense so highly that, despite his numerous flaws, the giant center-back was paired with Laurent Koscielny again.
There are obvious reasons why the manager would stick with his Teutonic rock instead of opting for the club captain. Vermaelen and Koscielny are very similar players: Both are relatively short in stature, fleet of foot, prefer the ball at their feet and have a tendency to go for the ball high up the pitch.
Mertesacker is the exact opposite. He is almost too slow to play in the Premier League, but makes up for his lack of physical speed with a quick mind. When he can read the game in front of him and position himself to deal with an attack, Mertesacker is very effective.
Though Vermaelen and Koscielny do this to some extent—they are professional center-backs, after all—they do not rely on reaction time so much that anticipating has become their craft.
Of course, Mertesacker's height confers him an advantage on almost any other defender and forward. He does not use all 6'6" of his frame to his advantage, but he is nevertheless Arsenal's best defensive header of the ball.
Let's take a statistical look at how Mertesacker has performed this season, relative to other defenders at Arsenal and different clubs (all via WhoScored.com).
In 29 Premier League appearances this season, he is averaging 1.5 interceptions per game. Rio Ferdinand, a staple in runaway leaders Manchester United's lineup, posts the same number.
Nemanja Vidic, Ferdinand's partner in central defense, averages 1.9 interceptions per game, but he takes many more risks than Mertesacker does. The former commits 1.1 fouls per game, while the latter only gets whistled 0.4 times per game.
In other words, Mertesacker is much more cautious and measured in deciding when to make a tackle or go for the ball, and is able to put up good numbers without sacrificing free-kicks. His red card against West Brom two weeks ago was an anomaly.
That said, Mertesacker is far from the best in the Premier League.
Jan Vertonghen is certainly up there. His 2.9 tackles and interceptions per game blow away his rival's 0.8 and 1.5, and he only commits 0.3 fouls more per game while being dribbled 0.3 more times.
Who is Arsenal's best center-back?
Mertesacker's more cautious style does not allow him to be one of the true elites at this level. Vertonghen's all-action style does. Re-watch the last North London Derby and count the amount of crucial tackles the Belgian makes. It's nothing short of remarkable.
Yet the giant German is Arsenal's best defender.
Remember that he is not only the Gunners' lone bastion of stability in the middle of a high defensive line, but also their metronome at the back.
He averages 51.8 passes per game, compared to Thomas Vermaelen's 44.8. And many more of those passes find their targets—91.9 percent versus 86.3 percent.
Mertesacker seems to do much more of this work when partnered with Laurent Koscielny. The Frenchman averages just 28.1 passes per game, and only 82.5 percent of those are completed.
Koscielny also lags behind Mertesacker in fouls (0.7 per game versus 0.4), interceptions (1.4 versus 1.5) and offsides won (1.1 versus 1.2). The latter is also true of Vermaelen (0.7 versus 1.2).
Allow me to translate this into plain text, for I am no Nate SIlver.
Per Mertesacker is the most consistent and reliable center-back Arsenal have in multiple facets of the game. While he is not spectacular in any one area, he offers things that no other defender on Arsenal's wage bill can.
And while he will never truly graduate into the upper echelon of Premier League defenders, the weekly question on Arsene Wenger's mind should not be whether to start Mertesacker, but with whom he should pair him.