Clarke Oduor was an unused substitute as Barnsley ended Brentford's 22-match unbeaten run after emerging 2-0 victors in their Championship game staged at the Brentford Community Stadium on Sunday.
Conor Chaplin and Carlton Morris struck in either half to hand the visitors maximum points.
It was the Reds who showed their intentions from the first whistle, pushing forward and pressing the Bees to ensure they struggled to get the ball in the final third.
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Barnsley's efforts were rewarded after just 13 minutes when Callum Brittain picked out Chaplin inside the 18-yard area and the latter bundled home from six yards to hand his team a deserved lead.