The Spaniard has been criticised for errors this season but Downing feels the goalkeeper is back to his best.
"It's hard for keepers. As players, we make many mistakes in games, but they get overshadowed by other things," he said.
"A keeper makes a mistake and it's in the back of the net. It is a tough position to play. But you see his save at 2-0 and if we had gone in 2-1 at half-time that would have made it more difficult.
"People don't tend to see that, but we as players could see it was an important save.
"It gave us the platform to go on and get the third goal and it was easy from then on.
"He's a top-class goalkeeper. Everyone has dips in form and things like that.
"It's about the way you bounce back and he certainly has."