Arsenal slumped to a fourth defeat in six Premier League games as Wolverhampton Wanderers shrugged off a worrying early injury to Raul Jimenez to claim a 2-1 win at The Emirates on Sunday.
Pedro Neto out Wolves the ahead in the 27th minute and although Gabriel headed the hosts level, a clever finish by Daniel Podence restored the visitors' lead before halftime.
Arsenal pressed Wolves back in the latter stages of the second half but they struggled to create clear chances.
Wolves hung on for their first league win at Arsenal since 1979 to move up to sixth in the table on 17 points, four points off the top, while Arsenal are languishing in 14th spot with 13.
Mexican forward Jimenez was involved in a sickening clash of heads as he challenged for an aerial ball with Arsenal defender David Luiz and required oxygen before being taken to hospital.
After a 10-minute stoppage Brazilian Luiz soldiered on with his head bandaged but did not emerge for the second half.
While describing it as a fantastic result, Wolves skipper Conor Coady said his first thoughts were with Jimenez.
"It was a horrible clash of heads," he said. "We hope and pray that everything's okay. The one thing that matters is that Raul and David Luiz are alright."
Wolves manager Nuno Espirito Santo confirmed later that Jimenez was conscious and undergoing a scan.
Former Arsenal boss Unai Emery was sacked exactly a year ago but, despite initial encouraging signs under Mikel Arteta, Arsenal have stagnated and this is now their worst start to a Premier League campaign following three successive home defeats.
After the shock of Jimenez's injury, Wolves refocused and went ahead when Adama Traore's cross was headed against the bar by Leander Dendoncker, with Neto alert to bundle in the rebound.
Arsenal responded quickly and were level three minutes later when Willian's pinpoint cross was met by a bullet header from Gabriel who gave Wolves keeper Rui Patricio no chance.
Wolves were always dangerous on the counter-attack though and a fluent move saw them re-take the lead after 42 minutes.
Again it was Traore causing havoc as he burst goalwards before finding Neto, whose deflected shot was parried by Bernd Leno before Podence brilliantly flicked the loose ball over a sliding Gabriel before firing home.
Arsenal had loads of second-half possession and Arteta sent on Alexandre Lacazette late on but they created little, with their two shots on target during the game a damning statistic.
(Reporting by Martyn Herman; Editing by Ken Ferris)
