The Gunners looked like easing to a comfortable win after Pierre-Emerick Aubameyang's sixth-minute opener, but seven minutes before the break Xhaka took a short pass from Leno and inexplicably kicked the ball against Chris Wood, watching in horror as it flew into the net.
It was another dismal moment for Xhaka, sent off in December when Burnley won at the Emirates Stadium, and his eighth error leading directly to a goal since the start of the 2016-17 season - the most of any outfield player in the Premier League.
But Leno says the tactical approach, playing out from the back, is one to persist with despite the error, and Xhaka was simply guilty of back luck.
“We wanted to build out again because it had been working and it was very unlucky from Granit but it happens," he told BBC Sport.
“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.”