For the second week running the Royals came from behind to claim a valuable win.
Adam Le Fondre's brace from the bench cancelled out Yohan Cabaye's opener, as Reading claimed their first top flight away win since 2008.
"It was a tough game, they got the goal - but I just felt we were in the game, came out second-half, made a couple of changes and the boy who came on did really well," he told Sky Sports.
"It was an important win. To win last week and today that gives us momentum and I have absolute belief in these players as I always have."
McDermott admits Le Fondre's two goals will put the pressure on him to start the striker.
"Adam wants to play, everyone does - it is all about the group and he understands that, and he knows he is doing what he needs to and I am so proud of the lads," he said.
The Reading boss also praised the performance of goalkeeper Adam Federici, who was particularly impressive in the first half.
"He made a couple of really good saves and when you come to somewhere like Newcastle you need your goalkeeper to play well," he added.