The French champions play Bordeaux on Sunday, one week after their embarrassing 3-1 defeat by Ligue 2 leaders Evian Thonon Gaillard in the French Cup.
Didier Deschamps' men lie in fifth place on 29 points, three points adrift of leaders Lille, and will need a refreshed Gignac to help them defend their title.
Since his 16.5 million euro transfer from Toulouse in the close season, the 25-year-old striker has managed just one goal in Ligue 1, raising doubts over his ability to deliver in a bigger club.
"I know that these first six months have not been brilliant and that I did not do everything I should have done," Gignac told reporters.
"I wasn't as professional as I used to be. On a lot of small details. I talked about it to the club, to my family. I have nothing to hide.
"Things were much worse at Toulouse my first season there. But I am strong," he added. "What affects me the most is the Velodrome (stadium). There are a lot of expectations from my club but also from the supporters. I wasn't up to it."
"At Toulouse, the team played for me, I was alone up front. At Marseille, we have a lot of attacking players that I need to adapt to."
"It is up to me to improve technically", he said.
Two seasons ago, Gignac was enjoying the time of his life at Toulouse, scoring 24 goals and emerging as Ligue 1's top goal-scorer.
Now he is booed on a regular basis by the fans at the Velodrome and has become a popular character on a satirical puppet show where he is often mocked for his weight and slowness.
Marseille ended the first half of the season by taking only four points from their last five league games and Gignac promised he would help the team up their game in 2011.
"I am convinced this club is made for me. I can't not succeed here. Otherwise I wouldn't have come. I had other proposals. I rarely doubt," he said. "I love this city and this town too much to stop at failure."
In other matches, Lille will try to increase their one-point lead at the top when they visit Nice on Saturday, while second-placed Paris Saint-Germain host Sochaux at the Parc des Princes.
Struggling Monaco travel to Auxerre for their first game under new coach Laurent Banide after Guy Lacombe was sacked following their humiliating French Cup exit against fifth division Chambery.
