The Brazilian's strike, which came from an offside position, bailed out Areola, whose heavy touch and botched clearance from a back-pass gifted Nicolas de Preville an equaliser four minutes from time.
It meant the 23-year-old did little to press his claims for retaining the number one spot, with Kevin Trapp set to recover from a thigh injury to face Barcelona in the Champions League next week, but France midfielder Matuidi was sympathetic towards his plight.
"We all make mistakes," he told reporters. "He is a young player. He has all of our trust and is a great goalkeeper.
"Sometimes we may be the unloved, then the hero the next day."
Head coach Unai Emery believes the keeper will be stronger for the experience.
"Alphonse is young. He needs experience," the Spaniard said of his 23-year-old keeper.
"I believe that living these negative things will help him for the future."
Lille midfielder Julian Palmieri was left aggrieved by the decision for Lucas' winner and claimed referee Francois Letexier apologised on his colleague's behalf at full-time.
"We know that the goal is not valid," he told reporters. "I saw Lucas' eyes when he scored – he is surprised himself the goal is allowed.
"He is not [offside by] fifty centimetres, but one metre. He is offside for all of the action.
"And the worst is that the referee apologises after whistling at the end of the game. It does not give us the point we hoped for or take away our frustration."