Coach Marcelo Bielsa blasted Marseille's form, despite their ninth win in 12 league games to go four points clear at the top, but goalkeeper Mandanda and striker Gignac were quick to hail their resilience.
Marseille came into the match after back-to-back losses to Lyon and Rennes - the latter in the Coupe de la Ligue - but built some confidence ahead of their showdown with second-placed Paris Saint-Germain in the capital on Sunday.
While Mandanda conceded his team-mates faded late against Lens, he also noted that he had only a few saves to make in the victory - though he did produce an excellent stop at the death.
"That save was important at the end, it was a decisive one," he said. "It was right at the end of stoppage time and we were struggling.
"I did not have much work to do, but could make a decisive save which makes me very happy.
"It's great for me and for the team. It was a good response because after two defeats in a row, in league and cup, we were able to win."
Gignac admitted that Marseille made some errors, but hailed Mandanda's late heroics to preserve their advantage.
"We knew how good Lens would be in the counter-attack," Gignac said.
"We put in a good defensive performance but also we scored quickly which normally helps make it an easier game for us.
"However, it did not help us this time, the opposite happened. We relaxed and made some defensive mistakes. We did not press them well. We gave them chances to score.
"They got more and more confidence through the game and started to be dangerous. It was then that they found an equaliser.
"In the second half, we came back more organised and were able to score that second goal.
"I have to say that Steve Mandanda made an extraordinary save on the last chance they had.
"Otherwise, we would have lost two points. To have a four-point lead at the top is very good and builds confidence for the game with PSG."
