Ivan Juric could now resign without problems or start making plans for his life with Southampton in the league.
This summer, the Croatian boss has a termination clause in the 18 -month contract he signed after Russell Martin, dismissed.
So if his continued involvement with Southampton depends on his Premier League status, he can do so. They have no chance of overcoming the fall.
Two goals in the second half (and one from a penalty) from Bryan Mbeumo while the plays of Keane Lewis-Potter and Yoane Wissa added to the score.
Kevin Schade’s first-half opener bagged Brentford their first Prem win on the road this season.
And if it had been for a shot from Wissa and Lewis-Potter, a great save from Aaron Ramsdale and the crossbar, it would have been more embarrassing.
Southampton are 10 points adrift of safety and that gap could expand further if Ipswich win at Fulham today or if Wolves get any kind of result at home to Nottingham Forest tomorrow.
Juric said: “It was a bad day. I am disappointed with everything.
“I expected more after two weeks here. I felt like we could compete and do better. But today I kicked you in the head. “
“The players know the situation is bad but we must try to get better.
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“I had never had this feeling before. There is a big difference between the teams.
“Today I thought we could take a step forward, but I stayed in three. We can no longer relive this day. We lost 5-0 at home.
Brentford enthusiasts taunted the Saints by chanting, “How must they be, we’ve drifted apart!”
And Chief Thomas Frank said: “It is one of my most important moments in terms of performances with Brentford in the Premier League.
“It is difficult to move to Southampton a team that is fighting for their lives with a new manager and energy. In winning the way we made it satisfactory.
“We had general control for 90 minutes. We haven’t revealed anything. We scored five and we deserved to have scored even more. I am satisfied and proud of it. The Saints were off to the worst start imaginable, trailing in the sixth minute.
Mikkel Damsgaard played a lovely pass into the path of Schade, who hit a lovely shot with the outside of his right boot to beat Ramsdale.
Then Yoane Wissa was denied doubling the lead by a point-blank save from Ramsdale.
Christian Norgaard met a Mathias Jensen corner, his header ricocheting off the bar.
Brentford thought they had doubled their lead after the break when Sepp van den Berg headed in from a corner.
But Wissa had brought down Jan Bednarek before the goal and referee Stuart Attwell overturned his decision after seeing it on the pitch monitor.
Wissa missed a shot from the goalkeeper after a header by Schade, but shot over the crossbar.
But they finally grabbed their second.
Mbeumo made a one-two with Wissa firing an indirect shot into the roof of the net.
And it got worse for the Saints when the clumsy Lesley Ugochukwu pulled the cold house Sepp Van den Berg and Mbeumo.
Wissa saw an effort in the corner kept through by Ramsdale and Lewis-Potter fired just an inch wide after being played through to Mbeumo.
But Lewis-Potter snatched a room at the time up after being installed through Mbeumo and there is still time for Wissa to load another after touching in a horrible header from Yukinari Sugawara to Head Housearray
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