Cech injured his left hamstring taking a goal kick just before half-time during Arsenal's 2-0 Premier League win over Watford at the Emirates Stadium on Saturday.
The 36-year-old keeper had retained the No.1 jersey up until then despite competition from summer signing Bernd Leno, who many assumed would quickly establish himself as first choice for Unai Emery.
The Arsenal head coach instead offered Cech the chance to keep hold of the No.1 spot, and the veteran impressed - in particlar during a 2-0 win over Everton - despite question marks over his kicking.
Unfortunately for Cech, the layoff means that he will definitely miss Arsenal's Europa League clash against Qarabag on Thursday before Sunday's Premier League trip to Fulham.
The international break offers Cech a welcome pause, but he could well miss Arsenal's first game back against Leicester on October 22.
With the Gunners facing a tough run of fixtures into early November including a game against Liverpool and two versus Sporting Lisbon, Leno has an opportunity to stake his claim to become Emery's regular starting keeper.
