Le Fondre cashed in on some woeful defending to score twice coming off the bench.
McDermott said: "Adam Federici pulled off a couple of really good saves in the first half which proved to be match-winning saves.
"Pavel Pogrebnyak had a real chance in the first half before they scored and we could have been 1-0 up.
"But you come here and they get to 1-0 up and then it's never going to be easy. But I thought in the second half, we upped our game.
"You have to manage games. You have to stay in the game and once Newcastle didn't get a second goal, we knew we were in with a shout the longer the game went on."