Chelsea will lodge their full appeal with CAS and are expected to request a 'fast-track' hearing, to which Fifa would also have to agree to.
Once the club has notified CAS of its intention to appeal, which must be done by tomorrow, they have a further 10 days to lodge the papers with them.
A one-window ban is unlikely to hurt Chelsea too much as they have carried out little business in January during previous seasons.
Meanwhile, goalkeeper Hilario is expecting to make way for Czech Republic international Petr Cech against Aston Villa on Saturday.
Hilario was impressive when he deputised for the suspended Cech in the 2-0 win over Liverpool at Stamford Bridge prior to the international break.
Hilario, who signed a new contract with Chelsea in the summer, knows that Cech will want his shirt back and has no complaints.
"I am pleased to be here," said Hilario. "I love this club, I like very much the people around and I love London.
"My family is really settled, my kids too and I want to continue here, I want to do good work."
Midfielder Michael Ballack is expected to be fit to face Villa after recovering from an ankle injury sustained on international duty with Germany.