Aston Villa's Premier League title ambitions suffered a damaging blow as an 11-game home winning streak ended with a 1-0 defeat to Everton.
Villa could have cut the gap on leaders Arsenal to four points with victory at fortress Villa Park, but they were undone by Thierno Barry's second-half strike.
Barry's 59th-minute winner came courtesy of a defensive howler by Pau Torres, a goalkeeping error by Emiliano Martínez and hands further initiative to the Gunners in the title race.
A frustrating afternoon highlighted how Villa are perhaps not serious title challengers given the fragile state of their squad and they will need some reinforcements in the coming weeks if they want to remain in the hunt.