The Argentine pair may be suffering from a gruelling domestic campaign, or perhaps the two players are being misused by national coach Alejandro Sabella.
Whatever the reason, though, neither forward Aguero nor full-back Zabaleta have replicated their stunning Premier League form so far in Brazil.
|Pos||Shots||Accurate Crosses||Shots on Target||Won Tackles||Successful Dribbles||Mins|
As Opta stats show, the City men are yet to deliver an accurate cross for Argentina, despite both taking up wide positions. In terms of shots, meanwhile, Aguero has hit the target with just one from five, while Zabaleta has only taken one (which went wide against Iran).
Indeed, it was during Argentina's second game against the Iranians that both players' shortcomings were exposed. Zabaleta was run ragged defensively, as is shown by his total number of won tackles being three times less than team-mate Javier Mascherano, with the 29-year-old almost giving a penalty away after appearing to foul Ashkan Dejagah.
It was the magic of Lionel Messi that spared Sabella's blushes against Carlos Queiroz's men, as a stunning late winner sent Argentina through to the next round.
But, by comparison, Aguero has struggled to find any sort of form. Messi has Aguero beaten in both the shots and crosses department, while his staggering total of 14 successful dribbles makes a mockery of Aguero's 0; Zabaleta, too, has beaten his man only once.
The opening win against Bosnia & Herzegovina was a similar story, with Messi again being responsible for both goals in a 2-1 win.
More will be expected from Argentina as they progress through this summer's World Cup, with many tipping them to go all the way in the tournament.
Sabella's tactics have already been criticised by Messi in Brazil, so it will be down to him to get more from the likes of the Citizens stars Aguero and Zabaleta.
They aren't the only ones underperforming, of course, but their quality and experience means that they will carry more and more responsibility with every game. A nation expects.