Meanwhile, after missing the last four games with a thigh problem Shkodran Mustafi has returned to full fitness but is set to miss the visit of West Ham.
Wales midfielder Aaron Ramsey is on course to return in the New Year after resuming running again after a hamstring problem, but Santi Cazorla is unavailable.
"Ramsey was out running [on Monday] but he will not be back in the next 10 days," said manager Arsene Wenger, according to the Arsenal official website. "For him, the beginning of January is more likely.
"Shkodran is back again. I will not use him on Tuesday but he's available again. Theo is 100%, he will play on Tuesday."
Walcott himself dropped a major hint he will be fit to return for Arsenal after posting a photo of him training with his team-mates ahead of the Carabao Cup tie.
Amid a run of nine games in the space of 29 days, Wenger admits some of his squad are "on the edge" physically, a predicament which will force him to rotate his squad for the visit of West Ham.
That is likely to see the Frenchman revert to the players who have been deployed during much of Arsenal's European and domestic cup campaigns, with David Ospina, Rob Holding, Mohamed Elneny, Joe Willock and Reiss Nelson all expected to feature.
Wenger will also have to choose between Olivier Giroud and Alexandre Lacazette in attack after both France internationals played against Newcastle.
"Some players are a little bit on the edge," he added. "I think as well that we have so many quality players who did not start on Saturday, so you cannot say that you prefer to play a player who has played three games in six days to a guy who is at the same level and is completely fresh.
"The players who will start are basically all international players, so that's why I think [squad rotation] makes sense. You have as well to show the trust and the confidence that we have in the players who did not start last week."