Mikel Arteta's men were in the ascendancy and the floodgates appeared to open with Pierre-Emerick Aubameyang's early strike, but the Gunners were once again the victims of their own downfall after failing to add to their tally.
While looking to play out from the back, Xhaka received a pass from Leno and attempted to play it out wide, but the Switzerland international instead hit the ball onto the chest of Chris Wood and was forced to watch the ball trickle into the back of the net.
There were no more goals to be had despite a dramatic finale and VAR controversy, and while Xhaka understandably came under fire after the full-time whistle blew, Leno has defended his teammate and Arsenal's style of play.
Speaking to BBC Sport, Arteta's number one said: "We wanted to build out again because it had been working and it was very unlucky from Granit but it happens.
"There is always risk to play out from the back but this is our style. I think we have more than enough situations where it works to our advantage."
The Gunners remain nine points adrift of the Champions League places following yet another setback at Turf Moor.