Brendan Rodgers admitted Liverpool's slow start was the deciding factor in a disappointing 2-1 defeat by Manchester United on Sunday afternoon.
An incident-filled meeting at Anfield saw the visiting side command much of a frantic opening period, punctuated by a side-footed conversion from Juan Mata after 14 minutes.
Rodgers introduced Steven Gerrard at the outset of the second half but within a minute the No.8 was walking back to the dressing room - dismissed following an incident with Ander Herrera.
The challenge increased further for the Reds when Mata grabbed his and United's second, contorting his body to lash a volley around Simon Mignolet and into the bottom corner.
Daniel Sturridge produced a clinical finish at the near post in front of the Kop and Mignolet punched away a stoppage-time Wayne Rooney penalty, but it wasn't enough.
Rodgers said at his post-match press conference: "We disappointed in the first half.
"Our game was set up to press the opponent really high up the pitch, but our starting positions were way too deep from the early stages of the game and we handed over control way too easy.
"Rightly they were in front in the first half, they circulated the ball well and we were never in positions to press well enough.
"In the second half, we went down to 10 men early on but the players showed why they have been on the run that they have, with their character and resilience and they were still in the game right until the very end.
"That was the message to them afterwards: I take great pride in that. Not so happy with the first half - it was a game where the first half cost us more than the second.
"In that system, you have to be able to press well and pass well. If you're not doing both elements of the game then, of course, it becomes much more difficult for you to be effective.
"And that's how it was in the game today. In the first half, we weren't passing it anywhere near well enough. Ultimately we weren't pressing either.
"Both sides of our game suffered. We just didn't play well enough. You have to accept that. It just wasn't our day."
United's notable edge in the fledgling exchanges, coupled with the opener from Mata, moved Rodgers to alter his system in an effort to restore balance.
Such a tactical switch worked perfectly at Swansea City on Monday evening, where Liverpool had clocked up a fifth straight win in the Barclays Premier League.
Again the Reds improved after the interval, belying their 10-man situation, but this time it wasn't enough to preserve their remarkable unbeaten streak.
"It was simpler than the system," the manager explained. "They were playing 4-3-3 and we were too deep on the sides to begin with.
"The idea was that we should have been 15 to 20 metres higher up the field in order to press the game.
"It was only in the last 15 minutes of the first half, where I had to manufacture the team into a diamond that forces the players to be closer, tighter and higher up the field, and then we started to make a better game of it.
"It's something that you don't have the time to let it happen or else you can be behind even more in the game. That's what you have to do as a coach, you have to try to adjust.
"I'm not one to sit and watch and let it evolve and lose easily.
"For the second half the players deserve a huge amount of credit because you wouldn't have thought they were playing with 10 men.
"We didn't go 4-4-1, we stayed with a back four, played with three midfield players and two front players. It left us a bit open on the sides but we were able to control that fairly well, yet still maintain that attacking threat.
"They have got experienced players that worked the ball well against 10 men. But certainly in the second half at least we made that fight of it."
The result dealt a blow to Liverpool's ambitions of earning a spot in the Premier League top four and with it qualification for the Champions League.
A five-point gap has now opened up, but Rodgers pledged that his team will look to immediately recover in the race with eight fixtures remaining.
He said: "It's a big challenge. But when I looked at the 10 games that were remaining, it was always going to be difficult to win all 10 of them.
"So we built in a loss and maybe some draws in that. We'd hoped it wouldn't be in this game against our rival. But it's still very much possible.
"It's five points between us and [United]. We've now got to recover and use this as the same springboard that we did in the last game.
"We went on an incredible run which has at least given us the opportunity and the chance [to finish in the top four].
"We didn't play well enough today, that's the reality of it. They played well, deserved the win and we'll go away now, recover and come back and look to win the next game."
Gerrard was dismissed within a minute of taking to the field as a half-time substitute as referee Martin Atkinson produced a straight red card for his foul on Herrera.
Following the final whistle, the captain gave a frank interview in which he accepted 'full responsibility' for his actions and the boss was pressed for his reaction to the decision.
"I think with Steven, it was purely [him] wanting to make the impact," replied the Northern Irishman.
"He's made his apologies for it. Of course, in a big game you suffer when you play with 10 men against 11. But it happened and it's great respect to the players who were on there that they kept fighting.
"In games like that, especially if it goes to 2-0 against 10 men, you can get overrun and you can end up losing more goals.
"But the players showed immense responsibility and spirit to keep going and to keep the game open right the way through to the very end."
He added: "[Steven] is a highly competitive player. He made a great challenge when he first came on [on Mata].
"It was probably our first challenge of the game, in all due respect. He's wanted to help the team so much. I won't criticise him because he's been brilliant in my time here.
"Sometimes these things happen. If you look at our team as a whole and how we play the game, it doesn't happen very much to our team. Unfortunately it did today. We'll move on.
"It's big of someone when they do get sent off to come out and apologise. Steven was probably a little frustrated watching us in the first half - we didn't make a tackle - and at least he was man enough to come out and make that apology."