Sam Allardyce admitted West Ham United's failure to create clear-cut chances in the final third had cost them dear in Saturday's 1-0 Barclays Premier League defeat at Everton.
The Hammers maintained their run of resilient, organised and disciplined defensive displays at Goodison Park, only to be undone by substitute Romelu Lukaku's crisp 81st-minute finish from Leighton Baines' low cross.
However, it was West Ham's inability to open Everton up in the hosts' own penalty area - added to referee Jon Moss' decision not to punish Gareth Barry for an alleged professional foul on Kevin Nolan - that left Big Sam feeling frustrated.
"That was the difference - the gilt-edged chance that fell to Lukaku, he put away," said the manager. "When we were in that position, on the counter-attack, we didn't find the type of ball that Baines found to get a get a clear shot at goal and put it in the back of the net.
"We had several opportunities, particularly the second half, but we couldn't produce a lot more effective deliveries to score a goal.
"Whereas our technique in the last four games has been absolutely spot-on, and we've scored lots of goals, this time it wasn't as good as it has been. Because of that, we lost the game.
"Even right at the death, we had the last free-kick of the game but the quality on the delivery wasn't there. Last game, we saw Everton very unluckily lose at Chelsea on the last free-kick of the game.
"Our quality was missing when Frank Lampard's quality wasn't, which is why they lost that game 1-0, even if it was unluckily so on the way they played.
"What we needed to do was produce that quality and we'd have got a 1-1. It wasn't there when it had been over the previous four games. It's my responsibility to get the lads producing that quality in the final-third, like they had been in those games, when we got four very big wins."
While Everton's winner was not disputed, Big Sam was left apoplectic by the referee's decision not to penalise Barry for appearing to tug back Nolan as he went through on goal midway through the first half.
"I was up and down like a lunatic because I saw it, but unfortunately the referee said he didn't, which is beyond me because I was in the same position [angle-wise] as the referee, but 50 yards behind him.
"I could see Gareth Barry putting his arms around Kevin Nolan and pulling him down. I have no doubt he was going to score, because he's scored five goals in four games and is through one-on-one with the 'keeper."
After an opening half-hour dominated by the home side, aside from the Nolan incident, Big Sam did make a big decision to replace Carlton Cole with Andy Carroll after half-an-hour.
The No9 worked hard on his return after a three-match suspension, troubling the Everton back four and flashing two well-struck 25-yard shots over Tim Howard's crossbar in the second half.
"Our hold-up play needed to be better because we did not counter-attack enough, bar the odd occasion, which was a very good breakout from a header from James Collins. Stewart Downing collected and, like I said, in the previous four games he'd have produced a ball and if had then, Matt Taylor was one-on-one with the goalie.
"Other than that, we were stuck in our own half, so I needed to get better hold-up play. I didn't think it was quite happening for Carlton, so Andy came on and we got more into the game."
The manager now has two weeks to prepare for the trip to Stoke City on 15 March, where he hopes his side will embark on another unbeaten run.
"We can do that, but we've got to wait a couple of weeks before we play the next game, which is a shame.
"We'd have all liked to have had a game next weekend and gone again, but Hull City being in the last 16 of the FA Cup means that game is called-off now."