Laurent Blanc's men moved to within one win of retaining the French title following Wednesday's 1-0 victory over the Ligue 1 strugglers at Parc des Princes.
However, PSG left it late to secure the points as Lucas laid on for fellow substitute Blaise Matuidi to slot past Jesper Hansen in the Evian goal in the 89th minute, after the visitors had played the final 30 minutes with 10 men as Kassim Abdallah was sent off for two bookable offences.
Despite the lethargic performance, Lucas insists the only thing that matters was to pick up all three points.
Speaking to the club's official website, he said: "It was a very difficult match, we didn't play very well.
"But the important thing is the three points. We still need three more points to be crowned champions and we hope to get them on Sunday.
"I am very happy to have provided Blaise with the assist. This team win is a real pleasure."
PSG will retain the league if they beat Sochaux on Sunday, though a fourth title will be confirmed if Monaco lose at relegated Ajaccio on Saturday.
