Director of Rugby Ruddock conceded his team had not hit the heights he had set for them and a series of errors had ultimately cost them.
"We're very disappointed, very disappointed," said Ruddock. "We go into our home games looking to win and develop a fortress mentality - but it didn't happen for us.
"We're frustrated as there were a lot of errors, we didn't perform to the levels we wanted to.
"We hadn't played well first half and turned around behind, after they had taken advantage of the wind. We got ourselves back into a position where we were 13-12 behind and needed to stay in that area and maintain field position and apply pressure. It was a crucial time and who scored next would probably press on and win the game.
"Obviously, they broke away and scored. It was a big moment when the scrap broke out in the corner and the penalty went against us. They got field position and then scored when the ball broke their way.
"We watched them play last week and the ball didn't break their way at times from some of the kicks, it broke for Toulouse and they went on score," he added.
"Today, obviously, Quins benefited from a kick through when it bounced of a heel or ankle and fell to them and they scored.
"But they deserved to win. They were the better team and much more streetwise than us and took their chances. We huffed and puffed and showed lots of effort, but if I am honest we have played a lot better in games against Leicester and Northampton when we put ourselves in the position to win games. We didn't do that today.
"We did fight-back, yet we weren't the better team and that is why I am so disappointed.
"If we are serious about getting up the table and really being a force we have got to win our home games. We have to nail down games like this, we should look to beat them at home and it didn't happen today."
Ruddock acknowledged that there was not much between the teams and admitted the intensity of recent European games could have counted against Warriors.
He said: "We talked about the intensity and whether it would work for us or against us - quite possibly it worked against us.
"We thought they could be a little tired and we would be fresh, but we lacked cohesion and continuity in our game.
"There wasn't a huge amount in it, that period when it 13-12 was the key time and they broke away to score, we had to play catch-up after that.
"We showed a little bit of fortitude to make sure we got the bonus point and we showed spirit to do that. But we weren't good enough for whatever reason, be that lacking the intensity of recent weeks or we lacking enough ability across the park to do it.
"We will reflect on that, but the reality is we didn't play well enough to beat them."
Noise levels had been cranked up inside Sixways during the game as home fans grew increasingly incensed with the visitors and penalties.
"When you play at home you want your crowd to get on the back of the away team, at whatever chance they get," added Ruddock.
"The couple of times that they did make a fair bit of noise about a couple of decisions were relevant. There were a few of knock-ons by Harlequins when people picked the ball up in front of the knock on.
"Normally I would expect that to be a penalty. Today the referee didn't feel that was justified and from one of those positions they scored a try.
"It is something we will look at, but it's not the reason we lost the game. We lost because we weren't playing to our potential and didn't play as well as we did against Sale or Leeds. If we had played as well as that we would have nicked that game."