The 25-year-old’s reckless mistake saw him pass straight to Mantalos who took it around the Liverpool keeper to double Greece’s lead, with the hosts eventually winning 2-0.
Parrott spoke on the mistake and defended the Liverpool keeper after the game.
"It's frustrating for all of us, there is nothing we can do. Everyone makes mistakes, Caoimh doesn’t make many," said AZ striker Parrott.
"Everyone in the dressing room is behind him, but I don't think he needs it because he's strong enough mentally to deal with it.
"Obviously, it's frustrating to give a good side like this chances, especially at that time in the game when we were coming back into it and creating good chances ourselves. It's difficult, but we have to move on."
Republic midfielder Josh Cullen also opened up on the loss which many feel simply isn’t good enough for such a talented side.
"After they scored so early in the second half, I thought from then on we were the team that looked more lively. We had more control in the game," he told RTE Sport.
"I think the first half wasn't good enough from us, we tweaked a few things at the break. Just disappointed to concede so soon after half-time and I think the boys showed good courage and bravery to come back and lift the performance again."
Ireland have won just one game in their Nations League campaign and will have to find wins against England and Finland next month if they want to stand a chance of finishing second.
