Arsenal could have drawn level with the other table toppers, but they forfeited their lead against Norwich in a disappointing display of football.
Arsenal wrestled controls of the early proceedings and got the deserved lead via Mesut Ozil, with Sanchez making the assist.
And with the first half running out Lewis Grabban grabbed the equaliser after spinning around Gabriel, who came on for the injured Koscielny, and slotted in the goal.
The second half wasn’t much to wrote about for Arsenal, who failed to trouble Ruddy at all, and matters got worse when Sanchez was forced off with an injury.
Arsenal are indebted to Cech, who made a wonder save to keep out an own goal and ensured a draw for the gunner.