David Moyes was left devastated after Sunderland conceded a controversial 94th-minute winner to West Ham United in this crucial basement showdown.
The Black Cats, rooted to the bottom of the Premier League, looked set for a hard-earned, but deserved point, on their debut visit to the London Stadium.
But there was a kick in the teeth at the death when Winston Reid fired through a crowd of players following a home corner in the fourth and final minute of stoppage time.
There appeared to be a case for an offside appeal with a home player seemingly in front of keeper Jordan Pickford, but referee Bobby Madley awarded the goal.
"I spoke to the match officials, they think it was onside, I thought it was offside," said Moyes.
"You can tell by his reaction because he [the ref] walked towards the linesman, he was aware there was a problem."
After enduring a difficult and, at times, torrid first half an hour, Moyes's side grew into the game and looked worthy of a draw until Reid's last-gasp left footer.
"The disappointing thing was the players deserved something from this game," said Moyes, whose side are now five points from safety following Middlesbrough's 0-0 draw at Arsenal.
"We are trying to build a bit confidence and we had a point.
"Of course, we should have done better at the cormner, we shouldn't have turned our backs.
"We needed a decision to go our way today and it didn't."
Wahbi Khazri had the best sight of goal at the start of the second half with Adrian diving to his left to save, while Jermain Defoe had a tame shot in the first period and fired over after the break.
Sunderland gave as good as they got in the final hour and while nit looking like getting a winner they also didn't look like conceding either.
"I don't think we played well in the first half and it took us a long time to get to grips with them and their system," said Moyes.
"But I think by the last 15 minutes of the first half we had got back into it and we did all right in the second half.
"We made some chances and I don't think we deserved the outcome."