Ayoze Perez gave Newcastle the lead only a minute in and added a second in the 78th minute.
The Spanish striker was brought back into the side by Rafa Benitez after missing Tuesday's win over Barnsley, and the Newcastle boss believes his performance demonstrates the strength in depth his squad boasts.
He said: "It's important for him, he did well and worked hard. I didn't play him in the last game, but he did a good job.
"It's good for him but also good for the team because it means we can change players and they can perform.
"It's another good win, because it's not easy to win in this competition. We played really well in the first half, we had chances and could have scored more goals but we didn't do it so we had to work hard in the second half
"It's important to keep confidence high and the only way is working hard. We know every game is difficult and we have to be ready.
"After the second goal we had more control. It was easy at the end but you could see the difficulty we had at the start of the second half."