McDermott rubbished suggestions Guthrie had been told to stay away from the club's training ground following his reaction to being left out ahead of Saturday's clash at the Madejski Stadium.
"There's no bust-up. He wasn't selected to play for the game," McDermott said. "So, I don't know where the reports are coming from. Danny was training yesterday."
The Royals manager confirmed he and Guthrie had spoken about the 25-year-old's exclusion from the squad but insisted there were no heated words exchanged.
He added: "I try to have a conversation with the players that are not involved and I did have a conversation with him."
But when asked if Guthrie, who joined Reading from Newcastle this summer, had been upset by his axing, McDermott said: "Listen, if players are not in the side at this football club, they support the players that are in the side - that's what's got to happen.
"You get paid to play when you're selected.
"And when you're not selected, support the players that are playing.
"That's what we've had over a long, long period of time.
"That's the culture of this football club."