Goals from Conor Chaplin and Carlton Morris clinched the points for the Tykes in an ill-tempered affair which saw the visitors end the Bees’ 21-game unbeaten run.
But Ismael was keen to keep his players focused ahead of their midweek game against Blackburn.
“We won but we have only three points,” he said. “For a few weeks we’ve performed well but not got the result, but all the time against the top sides like Norwich and Watford we have been very close. The game against Chelsea gave us a lot of confidence because if you play like that against them you can compete against any side in the league.”
He added: “This win means a lot because we said we needed to make the next step. How good you play is all very well but in football you need a result. It is not enough to perform against them, just be there and lose the game.
“In this division you can lose to anyone and win against anyone but you have to stay focused. We will enjoy tonight but the next game comes quickly.”
Ismael said his side were 11 points away from their first target, and added: “We have a tough schedule until the end of February, but Chelsea was a game-changer in terms of our mindset.
“Since I have been trainer here it was the best week. We have a way to play football and today was the result of three months’ work. Everyone knows the principle, what we have to do and the game-plan and it has given us more confidence.”
Chaplin opened the scoring after 13 minutes when he arrived late at the far post to slot home Callum Brittain’s right wing cross, as the home defence watched.
Morris stretched the visitors’ lead two minutes after the break when he fired home off the post after Bees defender Ethan Pinnock failed to deal with Daryl Dike’s low cross.
Brentford head coach Thomas Frank admitted his team’s 21-game unbeaten run was halted by the better side.
“We knew before that Barnsley would make it difficult,” he said. “We lost to the better team today, but it is how we react to it and how we bounce back that matters. Today there was no lack of effort and they put everything out there.”
“It was inevitable that we would not go the rest of the season unbeaten but I think we have been so consistent and so good.
Brentford: Raya, Dalsgaard (Roerslev 74), Pinnock, Sorensen, Henry, Da Silva (Jensen 74), Janelt, Ghoddos (Forss 74), Mbeumo (Fosu 64), Toney, Canos. Unused substitutes: Reid, Goode, Daniels, Zamburek.
Barnsley: Collins, Sollbauer (Sibbick 67), Helik,Andersen, Brittain,Palmer (Jordan Williams 77), Mowatt, Styles, Dike (Woodrow 56), Morris (Adeboyejo 56), Chaplin (Frieser 56). Unused substitutes: Walton, Kane, Oduor, Moon.
Referee: D Coote (Nottinghamshire).
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