Sunderland manager David Moyes questioned the penalty that sent Swansea on their way to a 3-0 win over the Black Cats on Saturday.
Jason Denayer was adjudged to have handled the ball in the box which resulted in the penalty which was dispatched by Gylfi Sigurdsson.
Speaking toSky Sports, Moyes said,"I'm frustrated we didn't play well enough. Swansea deserved the victory in the end but it turned on a big decision for me.
"There was very little in the game, and these games are so important. Whoever gets the first goal it can make a big difference and I'm not convinced it is the right decision. It did turn the game.
"My view of it was he goes to block it. He is not looking at the ball, he has no intention. He is two yards away from the ball - very difficult - so I think it is the wrong decision."
The defeat in South Wales left the Black Cats propping up the table and they next face league leaders Chelsea in the start of a hectic Christmas period.
Moyes said: "That's the way it goes so everybody knows the situation. We've been on a good run. We didn't play as well today as what we have done but nevertheless that is the way the league is.
"We won the other week 3-0 against Hull at home. Swansea today have beaten us 3-0 and it is going to be tight around that end of the league.Look, we are improving. Six weeks ago you would have said we were written off but we are back in it. What matters is where we are come May but we are certainly back in with a fighting chance."