Guthrie claimed McDermott had his favourites, some players were "guaranteed" their place in the starting line-up and things are "already better" under new boss Adkins.
Former Newcastle midfielder Guthrie, who joined Reading on a free transfer last summer, said: "I don't want to talk about anything in the past, I want to look forward now. We've got a new manager now and everything is looking a little bit better.
"I think some of the lads who were guaranteed a place in the past have to be a little bit sharper and for players like me it's a new chance under a new manager. It has a big impact on everyone.
"There's always a buzz around the place when a new manager comes in. There was this week even though Arsenal is a difficult place to come. There will be again this week and we've got an important home game (against Southampton) next week.
"I don't know if there were favourites under Brian McDermott, but there were players who played every week. When a new manager comes in, it's a fresh start for everyone.
"It's been a while for me. It was a difficult 90 minutes for me but just happy to be playing again. I've not really spoken to the new manager, he just named the team and I was in it. I was just happy to be in the starting XI.
"I want to get some games under my belt, start helping the team get some results because we're running out of games. We need some back to back wins. That would make all the difference."