Tottenham manager Mauricio Pochettino was frustrated that his side lost 1-0 to Manchester United on the basis of one mistake.
Spurs dominated the opening exchanges as United and their new signings struggled to make an impact, but Kyle Walker's own goal gave the Red Devils a first-half lead and they were unable to grab an equaliser.
Asked what his feelings were after the defeat, Pochettino said: "Very frustrated. Very disappointed because we played much better [than Manchester United].
"With one mistake, we gave them the opportunity to score. We scored the [own] goal and it affected the team.
"Maybe it was difficult to keep the same level and play in the same way but after the second half, we dominated and Manchester United only shot one time on target but I think we deserve more. This is just football.
"In the first 20 minutes we dominated the game and created a chance. After that mistake we conceded a goal. I think we created more chances and deserved more than to lose 1-0.
"I think we played well and a high level. But it's true that when you make a mistake when you have the player in front of you like Rooney, like Depay, like (Ashley) Young then will get a chance and score.''
Harry Kane failed to test Romero all afternoon and Pochettino admits he needs more firepower up front.
"Yes, this is very clear,'' he said. "We need to add more players.''
Walker's effort was the first time in Premier League history that the first goal of the season was an own goal. But the defender believes that Tottenham did not deserve to lose.
"We gave them a game today but we just lacked the goals," he told BBC Sport.
"I tried to stick my foot in the way so that he'd kick my foot instead of the ball, so it's a bit unlucky really as I'd made up a lot of ground to get there. We just look onwards and upwards to our next game."