Di Maria did not feature in Argentina's 1-0 extra-time loss to Germany in the July showpiece after sustaining a thigh problem.
The 26-year-old limped off in his country's last-eight win over Belgium and despite a desperate bid to play in the final - which saw him ignore alleged instructions from then-club Real Madrid not to be involved - he was ultimately unsuccessful.
Di Maria moved from Real to Manchester United for a British-record fee of £59.7 million in the close-season and is expected to play a key role in the club's new era under Louis van Gaal.
And he is not troubled by his failure to play in the final, saying it was not something that has crossed his mind, before adding that he viewed Argentina's campaign as positive.
"I don't think about that," Di Maria told Perform.
"I couldn't play the World Cup final. Those injuries happen in football.
"I played many matches last season and that [made me] get an injury.
"We managed to finish second but I think Argentinian people were happy. And we were too because many people had [no] confidence [in] us and we reached the final."
Di Maria's compatriot Marcos Rojo also made the move to Old Trafford in the close-season, joining from Sporting Lisbon for £16m.
Left-back Rojo impressed for Argentina at the World Cup and finally made his United debut on Sunday after the club's lengthy quest for a work permit was successful.
And Di Maria has tipped the 24-year-old for big things, adding: "Marcos Rojo [has] shown at the World Cup [that] he is capable.
"He did really well there and he deserved to come here. Hopefully he will be able to improve every day as he did at the World Cup and he will bring a lot of good things to United."
