The game saw Philippe Coutinho score his first goal for Inter, while Samuel Eto'o was also on the scoresheet.
“I knew that the second week of training across the ocean would be the toughest with long journeys and two games in as many days," said Benitez.
“These are experiences that are still healthy and help us to grow. In the first half we did everything wrong that we avoided in Baltimore against Manchester City, even if we actually created more chances than Panathinaikos.
“This was only the second test and we believe that we can do well. We realise it’ll be tough to repeat the success of last season, but we’re working hard.”