David Moyes says Sunderland should have emerged from their Premier League clash with West Ham with at least a point after conceding an offside goal in the 94th minute.
The Black Cats showed good resolve after a difficult start to the current season to hold the Toffees, but were undone in the final passage of play as Winston Reid fired home from the edge of the area through a crowd of players after being set up by Dimitri Payet from a short corner.
Hammers substitute Jonathan Calleri appeared to be in offside position, and in the line of sight of goalkeeper Jordan Pickford as the shot came in.
After the match, an incensed Moyes said: "It was a very harsh way to lose a game.
"I was pleased with a lot of what the players did today. It was always going to be a tough game – West Ham have some good players. We struggled for the first 20 to 30 minutes, but after that we did quite well and created some chances ourselves.
"We're very disappointed to lose the game."
He added: "I've looked at the goal back and I've confirmed to the referee that we believe it was offside. The referee believes it was not offside.
"You could tell by his reaction, he walked towards the linesman, so he was aware there was a problem with it.
"I thought we competed and did quite well. We are disappointed, the players worked so hard and we've dropped a point in the end.
"We had some big chances to score ourselves and we wanted to build some confidence."