Gibbs, 22, has been sidelined since October after groin surgery, and Per Mertesacker is set to be out for at least a month out with an ankle injury.
Thomas Vermaelen will fill the centre-back vacancy left by Mertesacker.
Alessandro Nesta, Pato and Kevin-Prince Boateng have returned to training for AC Milan and could start.
"Mertesacker's replacement will be the most natural," said Arsenal boss Arsene Wenger. "That means I will put Vermaelen back in the middle.
"Gibbs looks to be ready and I might start him, but I haven't decided completely yet."
AC Milan have had their own injury problems to contend with but coach Massimiliano Allegri is now close to having a full complement to pick from.
Former Arsenal utility man Mathieu Flamini, goalkeeper Christian Abbiati and defender Mario Yepes have also recovered from knocks, while former Barcelona, Inter Milan and Juventus striker Zlatan Ibrahimovic is back from a domestic ban.
"It's very difficult to say if they'll play or not because they've only done two or three training sessions with the squad so we'll have to see,'' Allegri said.
"What's certain is that seeing as Boateng has been out for four weeks, he won't start from the beginning and that's the same for Pato. But to have them available is a good thing.''

MATCH STATS

Possession50%50%0minsAC MilanArsenal

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