Kevin Schade, Bryan Mbeumo (2), Keane Lewis-Potter and Yoane Wissa struck the goals for the Bees.
Juric said: "It was an extremely bad day. A really, really bad game and it was such a difference between the two teams.
"I'm really disappointed with everything. With the team, with myself, with everybody. It's just two weeks of work but I expected more.
“That I can do it more with the team. After the last game, I had a good sensation that we can compete and with some things that we can do better.
“But today it was like when somebody kicks you in the head. It was a big difference between the two teams. In one against one, in acceleration, in everything.
"I think that a few times in my life, even playing with great teams, I didn't have that feeling where we are competing in everything less.
"It was like too much difference, too much difference. Against Fulham, it was good defending and a clean sheet in the end.
"We created chances a lot against West Ham, a little bit against Crystal Palace and today I was thinking about one step forward and we did three steps back."