The Reds lost 2-0 to Zenit St Petersburg last week but Lucas feels the manner of the triumph on the weekend will help the players push for a winning score in the Round of 32 in Europe's second tier club competition.
"We started the week thinking it could be a really good week for us," said the Brazilian midfielder.
"But we had the defeat to West Brom and then the Europa League loss but we have finished the week off in a positive way by scoring five goals and keeping a clean sheet.
"We know we still have to improve a lot but this victory will give us confidence going into Thursday to try to get through against Zenit.
"With the way we played over there, we created a lot of chances, if we do that again and take them then we'll have a great chance of getting through to the next stage.
"But we also have to defend well on Thursday because if we concede an away goal it will be very difficult for us.
"We have to make sure we go with a positive and offensive mentality but knowing that if we concede it's going to be very hard."