David Moyes lamented Sunderland's inability to hang on for a point at Manchester City on Saturday.
The visitors appeared set to spoil Pep Guardiola's much-hyped bow in the City dug-out when Jermain Defoe cancelled out Sergio Aguero's early penalty, but Sunderland were guilty of sitting too deep and were punished when Paddy McNair turned Jesus Navas' low cross into his own net with three minutes to go.
Moyes, himself in charge of the Black Cats for the first time in a competitive fixture in their Premier League opener, told BT Sport: "I didn't think we deserved it. We can't deny City were the better side but we did everything to make it difficult for them and for long periods we did a great job.
"When we got back to one each it was disappointing, we gave away a bad goal. We backed off Navas and allowed the ball to go across the six-yard box. We should have stopped that but didn't. I can't be critical though because the players did a great job."
Moyes was less understanding with referee Bobby Madley, who failed to spot Willy Caballero tip over Duncan Watmore's early header. Madley wrongly awarded a goal kick and less than a minute later Patrick van Aanholt brought down Raheem Sterling inside the area.
"I hope you've all seen the goalkeeper tipping it over at the other end?" he asked. "From our point of view, those small things [matter] as they scored 30 seconds later.
"We should have done better but you need some of those things to go for you. It was a mistake, nothing else."
Sunderland's pre-season has been seriously disrupted by the Football Association's protracted pursuit and eventual appointment as England boss of Sam Allardyce, the man who led the Wearsiders to Premier League survival last term.
And Moyes, who brought in Manchester United trio McNair, Donald Love and Adnan Januzaj during the week, admitted there was still much work to do.
"We are not ready yet and won't be for a while," he said. "I want them to build on what they did last season and do better than that but that can't be done in two weeks.
"We are short in several areas, we'll do everything we can to improve the team.
"I though Love did a great job and [Premier League debutant] Lynden Gooch did a great job as well off the left. If these young boys do well we are happy to promote them."