Otamendi played the full 90 minutes at centre-back in front of former City ‘keeper Willy Caballero, who was making his international debut.
Ever Banega and Manuel Lanzini scored the goals for Jorge Sampaoli’s side.
Manchester United’s Jesse Lingard scored the only goal of the game as Gareth Southgate’s side made it seven without defeat.
David Silva played 71 minutes as Spain drew 1-1 Germany in front of 50,653 fans at the Esprit Arena.
Gabriel Jesus started in Brazil’s 3-0 win over Russia in Moscow.
The striker, wearing the famous No. 9 shirt, played 65 minutes before being withdrawn with Brazil 2-0 in front.
In Zurich, Bernardo Silva started as Portugal beat Egypt 2-1.
Mohamed Salah gave Egypt the lead after 56 minutes, before Cristinao Ronaldo scored two injury-time goals to earn Portugal the win.
And Oleksandr Zinchenko was involved as Ukraine drew 1-1 with Saudi Arabia.
The 21-year-old played 65 minutes of the game in Braga before being replaced by Ruslan Malinovsky.