Gayle took his haul for the season to 10 with three goals in the first 27 minutes thanks to left-foot, right-foot and headed strikes as Posh held out for a precious 3-2 win.
"He's a very good player. He's better than I thought he would be," Ferguson said.
"He's technical, doesn't give the ball away, and makes clever runs. He's the real deal. There's no question about that.
"He will score goals. He's a goalscorer. I thought him and (Nathaniel) Mendez were a real threat today.
"I don't know if we should have been hanging on as it doesn't justify our performance in the first half, which was outstanding.
"To come here and be 3-0 up, and it could have been more. I thought my players were outstanding."