Manchester United were humiliated at Gtech Community Stadium as they were thrashed by four goals in the first half.
Josh Dasilva's strike from distance gave the hosts a 2-0 lead.
During an incredible first half in which they dismantled United in stunning fashion, Ben Mee and Bryan Mbeumo goals put Thomas Frank's side four up.
The defeat is United's seventh in a row on the road, their worst run since 1936, and the seventh time they have conceded at least four goals in a league game.
The task of lifting United's players in time for the visit of the Reds on August 22nd is not easy.
The visitors' defence crumbled in spectacular fashion against their high-pressing hosts as they were beaten by Brentford.
De Gea, who for so long has been one of United's most consistent performers, was left red-faced when he allowed Dasilva's speculative shot from distance to slip beneath him and into the net.
Two minutes later, after another United mistake, the Danes celebrated when Jensen missed from the free- kick.
De Gea's pass to Eriksen on the edge of the United penalty area led to Jensen stealing the ball and slotting low into the net to make it 2-0 for the Bees.
After falling two behind to Brighton last week, it was another stern examination of United's character, but it only got worse as they were hit twice in the space of five minutes.
The Bees took a four goal lead after 35 minutes when Mbeumo finished off a rapid counter- attack after controlling Ivan Toney's pass and curling the ball past De Gea.
The first two games of the season have shown the enormity of the task facing manager Ten Hag.
While much of the post- match discussion will focus on United's problems, they should be applauded for their approach and Execution.
They dominated from the first whistle, taking their chances to leave United in the dust.
Jensen robbedRonaldo inside the United half and gave the onrushing Dasilva. Dasilva sent a low shot towards the goal that De Gea was able to save.
The first half was a riot as the team ran riot. The impressive Jensen anticipated De Gea's risky pass to Eriksen and punished both players, before Toney used his height advantage to beatMartinez in the air and tee up Mee, who marked his home debut with a goal
The fourth goal showed the difference between the two sides. The ball was long to Toney after Jadon was muscled off the ball.
With United slow to react to the developing counter- attack, Toney slipped in Mbeumo, who shook off Shaw and swept the ball home to the delirious home fans.
With his players apparently in shock, Ten Hag's response was to introduce Raphael Varane, Scott McTominay and Tyrell Malacia at the break, but with his players apparently in shock, United were unable to mount a comeback that would have made a difference to the game.