The Reds were beaten 2-1 in the away leg of their Europa League quarter-final, but Lucas is confident they can turn things around in the second leg at Anfield.
"We are really disappointed. We started the game really well and scored an early goal," said the Brazilian.
"We created some chances - even when we went down to 10 men.
"Now we need to keep going and try to score the goal at Anfield that could send us through. We knew the away goal was important, so we still have hope of reaching the semi-finals."