The 29-17 win at Estadio Centenario was O'Connell's first experience of playing in Argentina and the Munster lock was not surprised that Ireland had to dig deep to win their first match since the retirement of Brian O'Driscoll. But he believes the RBS 6 Nations champions made it difficult for themselves with some basic errors.
"It was very hard going. We knew it was going to be physical, which it was. We didn't know we were going to be as inaccurate as we were. We put a lot of balls down and missed some tackles," O'Connell said. "They put us under a lot of pressure and it kind of thrived off our mistakes. We were unlucky not to score a try early in the first half; 30 seconds later we were lucky not to concede a try.
O'Connell said the key now is to put in another good week's work before their next match in Tucuman, northern Argentina.
"This gives us something to review over the next few days," he added. "Knowing (Ireland coach) Joe Schmidt it will be a very tough review and hopefully our performance will improve."