Brentford's 10-match unbeaten run at home came to a shuddering halt as Barnsley claimed all three points thanks to goals from Adam Armstrong and Sam Winnall.
The Bees were second best throughout the 90 minutes and none of those in red and white can be pleased with their performance against the Tykes.
Dean Smith knows his side must improve with west London derbies against QPR on Friday and Fulham the following week to come.
Below are five talking points to emerge from the Bees' poor home showing at Griffin Park.
Unbeaten run ends
Brentford have not tasted defeat at home for 10 games, with the 1-0 loss to Blackburn the last time they left Griffin Park with nothing.
It was a shame that, on a day when the club was celebrating their 4,000th game, they produced such an insipid performance.
The display lacked spark, guile and was too predictable for the Barnsley defence, who had clearly done their homework.
Another slow start, as previously mentioned in the loss at Newcastle and draw at Derby, was duly punished as Adam Armstrong opened the scoring on the half-hour before Sam Winnall secured the points in the second half.
Hogan's struggle
Scott Hogan is lethal when he gets the ball in front of goal but, when he doesn't have the ball, he does not offer enough to the side.
The first half was a case in point as he went too early on several occasions before stopping and ceding possession.
His frustration was clear for all to see and he picked a fight with Angus MacDonald towards the end of the first 45 minutes.
Referee James Linington could have shown the Brentford striker, as the instigator, a straight red card but opted to book the pair.
His day was summed up when he did beat the offside trap and fired wide in the closing stages.
Difficult day for Defence
Brentford have been resolute defensively at home this season but they were shaky for 90 minutes against the Tykes.
Yoann Barbet was at fault for the Barnsley opener, while the defence were carved open for their second
Harlee Dean was left on the bench after his suspension for five bookings with Andreas Bjelland partnering John Egan in the middle of the Bees' back four.
Dean has his flaws as a player but, as a leader on the pitch, he is second to none and he must come back into the side for the trip to QPR next Friday.
The defender loves derby games and understands the importance they are to the club so a recall is imperative.
Rare Hofmann appearance
At 2-0 down, Dean Smith brought on Philipp Hofmann for his first appearance in the league since the opening day of the season.
The German's style of play doesn't fit in with the formation Dean Smith deploys but he showed willing to give the striker a chance.
While he wasn't given a chance in front of goal, he made some good runs and gave the Barnsley defenders something different to think about.
Maybe with a run of minutes, he may yet show the fans what he can do but he remains a source of frustration at Griffin Park.
Sawyers jeered
Romaine Sawyers has failed to win over the Brentford faithful just yet and was jeered as his number came up with 15 minutes to go.
There are some who believe he's only in the side because of his relationship with Dean Smith and it is probably those people who cheered his withdrawal.
Bar one sloppy pass, Sawyers had worked his socks off but it just wasn't to be his day.
That said, jeering him as he was withdrawn is only going to harm, not help the Saint Kitts and Nevis international. There are some Brentford fans who need a scapegoat. In the absence of Dean, Sawyers appears to be next in line.
