Mikel Arteta scored Premier League leaders Arsenal's first goal in a 2-0 win over Crystal Palace on Saturday but was later sent off in the early kickoff in south London.
The Spaniard stroked away a penalty two minutes after halftime after Arsenal substitute Serge Gnabry was chopped down by Adlene Guedioura.
Palace, who parted company with manager Ian Holloway on Wednesday after losing seven of their first eight matches of the season, had few opportunities even when Arteta was red-carded on 65 minutes for a foul on former Arsenal striker Marouane Chamakh.
Joel Ward came closest for Palace when he struck the crossbar but Olivier Giroud settled any Arsenal jitters with a headed second goal late on.
Arsenal extended their lead at the top to five points although Liverpool can close it back to two later if they beat West Bromwich Albion at home.
Chelsea, who began the day on 17 points with Liverpool, face fourth-placed Manchester City, who have 16, on Sunday.
Image: Mikel Arteta of Arsenal celebrates scoring against Crystal Palace from the penalty spot during their Premier League match at Selhurst Park.
Photograph: REUTERS/Andrew Winning