This time last year, talk of Vincent Kompany’s inconsistency began defining his reputation, with the once vaunted central defender reduced to a precarious place among soccer’s elite. Now, with Manchester City undefeated in the league when the imposing Belgian is in the lineup, the debate about his value has gone silent. Whatever ground Kompany gave last year to the world’s best defenders, he made up during a dominant start to City’s season.

Unfortunately for City, performances like Monday’s 1-2 loss to Arsenal make that start evermore irrelevant. With an injured Kompany watching from the stands at the Emirates, City fell to their fifth loss of the season, leaving them six points off the pace atop the English Premier League.

But to imply results like today’s would be reversed by Kompany’s health would be to overlook another key absence. Yes, the team has yet to lose without their captain in the lineup, but as former Arsenal right back Bacary Sagna continues to deteriorate before our eyes, the absence of Pablo Zabaleta, the Premier League’s best right back, becomes more pronounced. Until Zabaleta joins Kompany in City’s lineup, the team’s title chase is stuck in neutral.

The goals City gave Arsenal illustrated it perfectly. The first (below) was an exquisite Theo Walcott finish from the left of the penalty area, a shot that seized on one, maybe two, feet of space Joe Hart had to give at his far post. From one perspective, it was an unstoppable blast, one for the best finishes you’ll ever see from Walcott. Yet it also a shot that shouldn’t have been so easy to line up. Perhaps in the face of more urgency from Sagna, or positioning that made it more difficult for the attacker to cut onto his right foot, Walcott still releases an unstoppable shot, but no defender should be content with hypotheticals.

Then there was Sagna’s countryman, Eliaqium Mangala, who continues to show he’d be better placed with a title contender in Italy, France or Portugal. Thanks to some quick and precise execution from Aaron Ramsey and Mesut Ozil, the 24-year-old’s demoralizing attempt to switch the ball to the right flank became Olivier Giroud’s game winning goal. But unlike Arsenal’s first, where Walcott’s execution some credit, Giroud’s winner felt thoroughly preventable. Had Mangala’s pass been better executed, or a safer decision been made in the first place, Nicolas Otamendi wouldn’t have been left pursuing Giroud into a vulnerable channel, left helpless to prevent Arsenal’s second goal.

To City fans’ lament, today’s performance isn’t an isolated case, even if Arsenal’s approach wasn’t as blatantly exploitative as Liverpool’s or Stoke’s. Whereas Reds’ boss Jurgen Klopp seemed to outline a game plan for a high pressure approach that would destroy City’s insecure defense, Arsenal declined to follow in Stoke’s footsteps and replicate that plan. Instead, the Gunners exhibited Wenger’s trademark lack of game-to-game flexibility, something that seemed destined to derail the team after City’s opening 30 minutes of control.

SEE MORE: Chelsea’ upheaval should have City thinking twice about swapping Pellegrini for Mourinho.

But then City reverted to their own trademark; at least, the trademark that’s come to define this season. Though the team’s had to deal with Sergio Aguero’s injuries, David Silva’s prolonged absence, Yaya Toure’s inconsistency and Wilfried Bony’s non-Edin Dzeko-ness, it’s been their defense – their inability to find answers among Sagna, Mangala, Otamendi and Martin Demichelis – that’s undermined their fall. Instead of continuing to boss an Arsenal team that went back to the counter-attacking approach that won them January’s meeting at the Etihad, City’s defense allowed the game to turn.

Strangely, the weaknesses on display at the Emirates are exactly the reason so pundits remain in City’s camp. With Kompany in the team, City hasn’t lost in 10 league games. When he’s out, though, City plays like this, allowing the difference between City and Arsenal to be reduced to his health. When he’s fit, the logic goes, City is the better team, with Monday potentially providing more proof.

Yet now, after another game of Sagna’s failings, Zabaleta’s absence has been shown to be nearly as important. Can City win the title if only one of Kompany or Zabaleta’s returns soon? Or, perhaps better put, how long can those two stave off their next injuries? If either miss a significant part of the season’s second half, can City surpass Leicester and Arsenal?

For Pellegrini, there are other solutions. Improved play through the midfield is the obvious one. There, though, the solutions are less obvious. A new balance may have to be struck, and with any change to their approach, City risk losing what they’ve already got.

At the back, they only need health, but until Kompany and Zabaleta return, it’s impossible to consider City on the same level as Arsenal.