Keane was left rueing Riley's decision on Saturday (Getty)

Television replays showed Chopra was onside before scoring and Keane was left rueing two points dropped in a critical match for the Black Cats.

"We did score, but the officials have disallowed it and I don't know why," Keane told BBC Radio Newcastle.

"He clearly thinks he's offside when he's more than level with the player."

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There was brighter news for the Irishman in the shape of midfielder Kieran Richardson, who lasted the whole 90 minutes of Saturday's trip to Pride Park.

Richardson had been a doubt but Keane admitted the injury situation forced his hand.

"The position we're in we had to ask players to put themselves through it," he said.

"Kieran trained really well the last two weeks. It was a lot less of a risk than when he played against Liverpool."