The champions and their opponents were level after the opening half at Headingley before the Rhinos ran out 36-6 winners.
"It was a tough one to start with and we knew it would be," McDermott told Sky Sports News. "For 60 minutes it could have gone either way.
"Although it was 6-6 at half time, I thought we were the more dominant team.
"I thought we were very good. You can't reach that level every week but you can maintain that effort."
McDermott signed an open-ended contract with Leeds before the match on Friday.