Rhinos ran in seven tries and kept their first clean sheet against Super League opposition since an 8-0 win over Salford Red Devils last June.
The win lifted Rhinos to third in Betfred Super League and left them on 20 points.
McDermott described Rhinos’ performance as “clinical” and he said: “The further the game went, the better we got.
“I didn’t think we were that far out in front of Warrington for the first stage.
“At half-time there wasn’t much in it at all, but Warrington gave us some possession - they dropped some ball.
“I won’t say that made it easy for us because then we’ve got to be good with the ball. The task for us was to do something with it.
“We did and that’s where we need to take a lot of credit for the second half. But I am just mindful we were playing a team who are not where we know they can be.
“They are having a tough season and we will judge it accordingly. We’re really pleased not to have a try scored against us, but at the same time we beat a team that’s lacking confidence and not as good as they can be.
“In the first half especially I didn’t think we were crash hot and what I am trying to get across is I didn’t think we were brilliant and unpicked a very, very good team that’s on the money and we had to do a lot to break them down.
“We unpicked a team that can play a lot better than that and dropped a lot of ball and gave us a lot of possession.”
McDermott felt his team’s goalline defence early in the game laid the platform for their win.
“We kept repelling what they threw at us,” he said. “On top of that we were good with the ball as well.”
Hooker Matt Parcell led the way for Rhinos with a hat-trick. McDermott observed: “He has been good for us since he came here.
“He hadn’t had a pre-season. We’re at round 15 now and it takes a bit of getting used to each other. There’s still a bit of improvement in him, but he will enjoy moments like that and when he went on Rob Burrow posed a massive threat for us.”
Two injuries marred Leeds’ win. Ashton Golding suffered a hamstring strain and Brett Delaney was in a brace and on crutches following the game after twisting a knee.
Liam Sutcliffe moved to full-back when Golding went off and McDermott said: “They adapted very well.
“Sutty has played a lot at full-back for us and the try he scored on our right hand side in the first half took some scoring.
“He kept [Ryan] Atkins guessing with the way he carried the ball. The fact he’s played a lot at six helps him when he goes to full-back.
“I don’t know what his best position is. He has been very good for us as a left-centre, he can play full-back and does it really well and he had a fantastic run as a stand-off in 2015 and played a lot of games there in 2016.
“He is a good player. He wants to play six, but he will play anywhere as well - he’s a team player.”
McDermott also praised winger Tom Briscoe, who had been taken off after a series of mistakes in last weekend’s loss to Castleford.
“He was very strong,” said the coach. “It was a difficult week for him last week and for him to respond like that, he is a mentally strong bloke.
“I knew he was going to be good. I knew there would be a reaction - his task is to continue doing that.”
Another player singled out for praise was forward Jamie Jones-Buchanan, who McDermott described as the “ultimate competitor”.
He said: “I think he has been great this year.”
Rhinos are back in action on Monday when they visit Widnes Vikings. They are at home to Leigh Centurions four days later.