The 40-year-old gave Gus Poyet's men the lead with an own goal in first-half stoppage time but feels that a free kick awarded in the build-up should have been given in United's favour instead.
Nemanja Vidic equalised for the visiting side shortly after half-time but the Black Cats were later awarded a soft penalty for a clumsy foul by Tom Cleverley, which Fabio Borini ruthlessly dispatched into the top corner.
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"It was just one of them nights. It's getting laughable now, the decisions just aren't quite going for us," the Welshman told MUTV.
"We were quite happy with our performance - we felt we at least did enough to get a draw out of the game - but it wasn't to be.
"I thought both decisions were harsh. The first one, I was getting ready to jog up the pitch because I thought it was a free kick to us. Saying that, we've still got to defend the free kick and we didn't do that correctly so we got punished for that.
"It just didn't go for us today but we'll keep plugging away and look forward to the second leg - we're still in it and we'll look forward to the game at Old Trafford."