"We are disappointed with the result and more so with our performance, we were not up to par," the 34-year-old told UEFA.com.
"Unfortunately we made mistakes that cost us goals and we go home with bitterness, knowing they were better than us.
"As a big team and for what we represent, we must give our all to try and turn the result around, but it will be difficult against a team like Levante. But we owe it to our people for all the support they give us. We have amazing fans who support us in difficult times."
The return leg takes place at the Karaiskakis Stadium next Thursday.