But they saw the Ospreys run in five tries in their 34-9 victory - Aisea Natoga notching a hat-trick while Ashley Beck and Rhys Webb also added their names to the scoresheet.
Gareth Davies slotted three penalties for the Blues but they have now lost five straight RaboDirect PRO12games.
And John says Cardiff have to improve ahead of their clash against Ulster this Friday.
"I think the first four or five times we had the ball in the first half we gave it straight to the Ospreys," he said.
"And they scored three tries from it so you're chasing the game and they're a top quality side and you can't do that.
"We've got to work hard. We play against Ulster next weekend, it's a home game and we've got to come away with a bit of passion and show a bit of pride in the jersey they're wearing and pride in their own performance - that's the main thing."
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