Right-back: Danilo (Brazil)
He hasn't made a goal contribution since registering an assist on matchday one, but Danilo is still an important figure down the right for Brazil.
His penchant for driving forward and joining up attacks is crucial in creating openings in opposition defences. The Juventus full-back also has a cross or two in him.
Centre-back: Marquinhos (Brazil)
While Thiago Silva hasn't retired, the shift in power in Brazil's defence has already started, with Marquinhos turning into a real leader at the back for them.
Elegant on the ball, intelligent and an excellent reader of the game, the PSG star is among the best in the business, and carries an offensive threat from set-pieces.
Centre-back: Cristian Romero (Argentina)
Cristian Romero only made his international debut in June this year. But he hasn't looked back since then, starting in all of Argentina's qualifying games so far.
He possesses an excellent positional sense, and tracks his markers superbly, while using his tall stature to pose a threat from set-pieces.
Left-back: Alex Sandro (Brazil)
Much like Danilo, Alex Sandro's attacking output hasn't been impressive either, but he continues to make powerful runs forward and lay crosses.
The Juventus full-back has started all of Brazil's qualifying games bar one. His pace, athleticism and directness could pose a huge test of Argentina's mettle.