Cech injured himself on the stroke of halftime, pulling up after taking a goal-kick and being replaced by Bernd Leno - the summer signing making his Premier League debut. However, the German will get more chances to shine, with Emery saying Cech is expected to be out for two to three weeks.
The Wales worldwide, 27, arrived at Arsenal in 2008 and has made more than 300 appearances for the club.
The Gunners are then back in action against Leicester on 22 October.
Kings, Suns Willing to Help Facilitate Jimmy Butler Trade
Butler has yet to attend a Timberwolves workout and wants to sit out until the franchises executes a trade for him. Keep in mind, this is all for a disgruntled player with only one year left on his contract.
But that deal has now collapsed despite manager Unai Emery having made the 27-year-old - Arsenal's longest-serving player having been at the club a decade - an integral member of his new-look team. I want to have also the best preparation for him, for his mentality and his quality, to give us our best performance to help us to win. Leno can learn by staying near with Petr Cech every day. But like Everton, Watford had plenty of chances to take the lead and Emery said his team must still find ways to dominate games better.
"Although it is very hard to do - the hardest decision of my life - I believe that, after 10 years, it is the right time to step aside to allow new leadership, energy and ideas to take the club forward into this exciting new era". But this passion is necessary today.
Lucas Torreira, booked in the first half for a late challenge on Deeney, played in Pierre-Emerick Aubameyang whose cross was headed wide by Lacazette. "We need to continue being calm, and giving them calm".