Eddie Howe bemoaned a lack of a "killer touch" from his players as Bournemouth became the first team this season to lose to Sunderland in the Premier League.
Howe thought the Cherries would go on to win after Steven Pienaar was sent off for his second bookable ofence just before the hour when the match stood at 1-1.
But it was Sunderland who scored when Duncan Watmore put Victor Anichebe through, only to be brought down in the box by Adam Smith, Jermain Defoe sinking his former club with an expertly-taken 74th-minute penalty.
"We had a really good 15-minute spell [after the red card] for 15 minutes when we battered their goal and dominated the ball," said Howe. "They could not get out of their half.
"We needed to capitalise and find a killer touch to go on and win the game.
"Unfortunately we left the back door open and conceded a disappointing goal."
Howe said he did not disagree with either of Mike Dean's big calls - the red card for Pienaar and the penalty award against Smith.
"I have no complaints about the decisions," he said.
Instead, his complaints were against his side for failing to convert their "gilt-edged chances"
The Cherries boss said: "It was a frustrating afternoon. First and foremost I felt we should have been 2-0 ahead, we had really good opportunities in the first half which we didn't take.
"Then they got back in the game - but you felt the red card would swing it back in our favour. That's when we needed to find the killer touch."