McDermott told BBC Berkshire: "During the last 18 months you've seen we know how to win if we're not playing well.
"Losing 1-0 at half-time, the most important thing is to come back and win and they've done that."
The Royals saw off Swindon on Saturday after Shane Long scored from the spot following Alex Pearce's own goal put the visitors ahead.
Mathieu Manset added the winner with a 71st-minute header and McDermott singled out his big striker for praise afterwards.
"It was a fantastic finish. He has so much power and if you look at his frame now he's so different, we're getting him fit and he's lasting the game longer," he said.
"He had three chances on goal today; the stats are that if you have five chances on goal generally you score one.
"I told him that instead of worrying about the two that he's missed. What's important is that he won the game for us."
Centre-back Bongani Khumalo made his first start for the Royals since arriving on a season-long loan from Tottenham Hotspur, and McDermott was pleased with his contribution.
"It's the first time he's played for us and I think he did well," he said.
"It was a very good combination [with Alex Pearce] and he played 70 minutes so I was very pleased."
The Reading manager also had praise for Swindon Town counterpart Paolo di Canio, appointed to his first managerial role at the Robins in May 2011.
"He's got them really well organised, especially in the first half they were very difficult to break down, so we had to really step up which was good for us.
"He's an engaging manager, you can see that the players want to play for him and I hope he does really well."
In their previous friendly match the Royals beat Bristol Rovers 2-1 at the Memorial Stadium on 29 July.
Source: BBC Sport