Tyrick Mitchell scored a late own goal, firing back towards goal without looking and Henderson was unable to stop it finding the backof the net as West Ham cut the deficit to three goals.
The Spaniard found the backof the net three times in the space of 47 minutes in a dominant display from Arsene Wenger's men. Alex Iwobi added a fourth for Arsenal before Seydou Doumbia pulled one back for Basel.
Isak wouldn't miss a second opportunity though, with the former Real Sociedad goalscorer reacting quickly to a rebound in front of goal and placing a shot into the backof the net.
The Egyptian carried his run and kept his composure to slot the ball into the bottom corner of the Chelsea net. Chelsea battled back and grabbed an equaliser through Willian whose cross lobbed Simon Mignolet.
Arsenal wasted the chance to go top of the Premier League as West Brom fought back from a goal down to beat them at The Hawthorns. The visitors took the lead through Olivier Giroud, who headed in Mesut Ozil's free-kick from the right.
Barca came back with urgency after the break and eventually equalise thanks to a mistake by Rayo defender Lejeune, who sent the ball into his own net with the tip of his boot as he tried to clear a cross in the 82nd minute.
After back-to-back 3-0 defeats against Manchester City and Newcastle, questions were increasingly being asked of the manager, and eyebrows were raised before kick-off when Marcus Rashford was left out of the squad.
Spurs applied pressure as they looked to get back into the game, with striker Harry Kane striking the foot of the post and Ben Davies forcing a good save from Thibaut Courtois.
First, Diaz sprayed a ball wide to Joe Gomez before running around the backof the defence into the area to meet the right-back's cross and steer his header into the net.
Bu Deportivo fought back just after the hour mark when Joselu blasted into the top corner from the edge of the box. Two minutes later, Depor were 2-1 up.