 His first goal for the club was in a 2–3 defeat to Zulte Waregem in the final group game of the UEFA Europa League.On 28 February 2018, Lucas missed a penalty during the penalty shootout in Lazio's match against Milan in the semi-finals of the Coppa Italia; which Lazio eventually lost 4–5.On 15 March, Lucas scored the opening goal in a 2–0 away win over Dynamo Kyiv in the UEFA Europa League round of sixteen second leg, securing a 4–2 aggregate win and advancement into the quarter-finals of the tournament.