Martin O'Neill concedes he thought his Sunderland side had got the job done at Upton Park prior to Kevin Nolan's goal in the final minute that rescued West Ham a point.
Steven Fletcher's fourth goal in three games since joining Sunderland from Wolves had looked set to earn the Black Cats a first win of the season when he capitalised on a misplaced James Collins pass in the ninth minute.
After that, the Black Cats were under siege but could still have put the game to bed with chances on the counter-attack wasted by David Vaughan and James McClean.
In the end, Sunderland had to settle for a fourth consecutive Premier League draw courtesy of Nolan's late intervention.
"I am obviously disappointed," manager Martin O'Neill said. "We looked as if we had dealt with just about everything that had been thrown at us but we were never able to kill the game off.
"We had some great opportunities in the second half. West Ham were pressing forward and leaving the door open for us.
"We should have taken advantage of it. We should have won the game."
O'Neill was again quick to praise the performance of Fletcher, who many felt could struggle to justify the record transfer fee Sunderland paid for him.
"Fletcher is playing brilliantly for us. He has scored all of our goals so far," add O'Neill.
"He is bringing players into play, he is proving himself an all-round high quality centre forward."