The GUINNESS PRO12 league leaders were beaten 22-10 at Parc y Scarlets as tries for John Barclay and Liam Williams, as well as 12 points from the boot of man of the match Rhys Priestland, were enough to see them off.
Dan Evans scored the visitors' only try with 12 minutes left on the clock but a stern Scarlets defence ensured it was not the start of a dramatic fightback.
And Gibbs conceded the damage had already been done by that point, as the Ospreys left themselves a mountain to climb.
"I think first and foremost you've got to give credit to the Scarlets," he said.
"I think they were pretty good in most aspects of the game. They put a lot of pressure on us and forced us into errors we don't normally make.
"Secondly, we probably didn't turn up with enough intensity, even though we did talk about it. We knew what was expected of us but we didn't turn up with enough.
"We made crucial errors. You look at the set piece, some of the stuff, the scrum stuff and the line-outs that we needed to win, and we didn't. That's probably the tale of the game really.
"It's disappointing, and fair play to them again, they've gone and done their homework and I thought their set piece was a lot better, particularly the lineout, this week.
"That allowed them to get a platform into the game. We didn't get our set piece, our scrum right, and we've got to make sure we get that bit right.
"We knew that coming down here is tough, it's a hell of a tough place to play.
"We knew all that was in front of us, we knew what we needed to do what works for us and, when we play well, what we are doing, and we just didn't do that tonight. Fair play to them, they've turned up and done it."
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