Just months after competing in the Championship play-offs, the Bees were humbled by League Two opposition at Griffin Park.
Liam Sercombe, Danny Hylton and an exceptional long-range Kemar Roofe strike put Oxford three goals up inside 12 minutes – a deserved lead they extended through Jon Mullins to wrap up a 4-0 win.
It was a fitting start to a season which marks the 30th anniversary of the Yellows’ League Cup win at Wembley and a result Brentford manager Dijkhuizen could have no arguments with.
“It was an embarrassing performance from my team,” he said. “After 12 minutes it was nil-three and game over.
“It was a long night for me but also for the crowd especially and for my players.
“There were a lot of lessons tonight for me and for the players. That’s a good thing. The bad thing is we played awful.”
Brentford were booed off at the final whistle and back-up goalkeeper Jack Bonham was jeered by his own fans, having gifted goals to Hylton and Roofe.
Dijkhuizen was unhappy with a number of his players, although accepted partial blame having made 11 changes from Saturday’s last-gasp 2-2 draw against Ipswich.
“I have a lot of reasons make a lot of changes,” he said. “We had some sick ones Sunday, with Harlee Dean and Alan Judge.
“Jota was injured and we have a problem also with Andre Gray – is he going or not? I only had one striker and he played 95 minutes.
“Finally, you have a lot of changes and maybe too much. Maybe it is a good lesson for me so I learned a little bit myself.
“And I was surprised that there was no leadership in the team tonight.
“I think there was a couple of experienced players in the team and they didn’t show leadership on the pitch so I was surprised by that.”
The mood of Oxford counterpart Michael Appleton understandably contrasted with that of the Dutch coach after such an impressive victory.
“We were all frustrated after Saturday (and drawing at home to Crawley) and I asked for a quick start,” he said.
“We looked at the video from the Ipswich game and they pressed them really hard to get their rewards. I am absolutely delight for them.”
Roofe will be focus of much of the post-match attention after scoring an exquisite third, taking aim from 40 yards after the Bees back-up goalkeeper Bonham strayed off his line.
“It was a fantastic finish – a goal in a million,” Appleton said.
“I am sure it will be all over the TV and be one of the contenders for goal of the season already.”