The 23-year-old England international stubbed his toe on a door during the night, fracturing it and further delaying his return after a groin injury had already limited his availability this season.
"He is available to start and to play," Maresca told reporters.
"Everyone is happy, the teammates are happy, we are all happy and the most important thing is Cole is happy because a footballer wants to play games and make the sessions every day."
Palmer has only made four appearances for Chelsea across all competitions this campaign, scoring twice. Since joining from Manchester City in 2023, he has recorded 45 goals and 29 assists in 101 matches for the West London club.
"He is our best player, we are happy he is back, we need to give him time to be 100% fit. He has done fantastic in the past and no doubt he is going to do very good for this club in the future," Maresca said.
Too early for title talk
Chelsea find themselves in second place, with 23 points from 12 matches. Despite their standing, Maresca remains cautious about title aspirations.
Around this time last year, the Italian had said Chelsea were not in the title race. They eventually finished fourth last season.
"Too early in any case, if we win or don't (against Arsenal)," Maresca said. "Still end of November, still five, six months to go. More important in February, March, then from there we decide if you can achieve something important.
"I think is for sure different to one year ago. We spend one more year together. We went through a moment where we can learn from that moment.
"But it is still very early. Important to be where we are now in March, April and then we will see."
