Although David Luiz and Pierre-Emerick Aubameyang efforts eventually gave the Gunners the win, Leno had a few more hairy moments, shanking a number of clearances and looking nervy in the Arsenal goal.
"Having let Martinez go, who was magnificent, to see Leno making these types of mistakes, you wonder whether it was the right call," Keown said.
"It was a difficult night for Leno. The team had their backs to the wall but showed very good character to get back into it.
"A couple of changes were made. I thought when they changed it actually and went to a back five, the pictures then became more familiar to the players and they found a way to win this match."