David Luiz was sent off in the closing stages as Arsenal held Chelsea to a 0-0 Premier League draw at Stamford Bridge.
Both sides were left to rue missed first-half opportunities in a match between two London rivals that failed to catch fire.
The Gunners had the better of the opening half and should have gone into the break ahead when Aaron Ramsey hit the post and Alexandre Lacazette somehow fired over from the close-range rebound.
Chelsea had earlier missed a one-on-one opportunity from Pedro, who was foiled by Petr Cech.
The second half lacked the excitement of the first and the introductions of Eden Hazard and Alexis Sanchez from the two substitutes' benches did not provide the desired spark.
And David Luiz saw red for a high challenge on Sead Kolasinac with three minutes remaining, marking the third straight match Chelsea have had a player sent off against Arsenal and rounding off a poor performance from Antonio Conte's men.
Chelsea's run of five straight home league wins over Arsenal is ended by the draw, which leaves the champions three points behind Manchester City.
Arsenal have now won just two of their first five league games this season. The point means they remain three adrift of their rivals and six off Manchester City at the top, having now gone 14 matches without beating a top-six team away from home in the top flight.