The Whites led 1-0 against NK Domzale in Slovenia with a goal from Dominic Poleon, who also hit the post, and looked to be on course for their third straight pre-season victory, but late strikes by Slobodan Vuk turned the game round with the hosts winning 2-1.
McDermott, who again used the game to look at formations and tactics as well as build up fitness, said: “I thought we were good for the first 30 minutes or so.
“But we played in front of them in the second half, we didn’t flow with the ball and they pushed up on us.
“Sometimes you have to win ugly in games and I said that to them in the dressing room afterwards.
“We have trained hard, but it’s about winning games. We’re Leeds United and we have to win games.
“Results matter and fans want to see us getting results. I said to the players you have to have a results mentality.
“You have to stop the cross or the square balls in and we’re a long way from where we will be on August 3.
“From that you will learn that you have to do that in games at Barnsley or Huddersfield or wherever and grind out a 1-0. You do that, and we get the points, and the fans go home happy.
“I’ve been really pleased with them as a group and I can’t fault them, but it’s good to get reminders.
“You want to learn your lessons now. You have to make your point, you can’t gloss over it.
“There’s 46 games in the Championship and they have to be hard fought and relentless. They’ll listen. They’re good guys and good people. These guys will be winners.”
Leeds are next in action on Tuesday against Ferencvaros as their Slovenian tour continues.