Rhinos ran in 10 tries to confirm a place in tomorrow’s semi-final draw and McDermott said: “It was a good workout for 40 minutes.
“We didn’t pull away until they had a player sin-binned.
“Credit to Featherstone, they stayed with the pace of the game and pushed us a bit.”
McDermott added: “We scored some good tries against a tired defence.
“The fact we worked hard until the end to keep them out was good.
“It is exciting to be in the semi-finals. We are 80 minutes away from Wembley and I am pleased for the players.”
Rovers coach Jon Sharp had “mixed emotions” after the game.
“There’s disappointment in there, but also some pride,” he said..
“There’s a bit of frustration because I know we can play better, but at the same time I was really pleased with the attitude of the players.
“They battled away right to the end and that makes me proud. “
He added: “At one stage we were at 41 per cent completions and they were in the high-80s. The boys tried really hard and defensively we worked well even though the score blew out at the end.
“There are lessons to learn. Leeds were patient and we were a bit erratic at times.”