Brendan Rodgers acknowledged his frustration and admitted Liverpool were below par following their 1-0 defeat to Southampton at Anfield on Saturday.
The Reds suffered their first defeat of 2013-14 as Dejan Lovren's second-half header secured three points for the visitors.
Afterwards, Rodgers was honest in his appraisal of his side's performance.
He told his post-match press conference: "I think both [the result and performance] were very disappointing, in all honesty.
"We never really got going from the off - it was a bit lethargic and technically we were short today, so it was a very disappointing result and performance for us.
"As I said, technically, I was really disappointed today. I thought we never really got going and we were flat and slow in our game.
"Which hasn't been like us. We've normally started games very well. But we'll just put it down as one of those days and now we need to go on another good run."
Rodgers elected to select a back four consisting of Kolo Toure, Daniel Agger, Martin Skrtel and Mamadou Sakho for the contest - and reporters quizzed the boss on his reasoning.
He explained: "It was really what we had available. We've got Glen Johnson out injured and Martin Kelly's only returning - he's had a few games, but he's still trying to work up his fitness having been out for a year.
"Jose Enrique is one we've got to keep an eye on his knee. He's got an issue with his knee and if there is an overload on that, it could maybe put him out longer term. We've got Cissokho out already, so it [Enrique's knee] was one we needed to keep an eye on.
"Kolo and Mamadou have played at full-back before, but obviously you lose a wee bit of that offensive threat. They coped as well as they possibly could.
"I thought Toure was exceptional today with his enthusiasm and drive to try to get into the game.
"But I just felt from the off we never really got going and then to cap it off we gave away a really poor goal from a corner.
"In the build up to it, we conceded possession poorly and then ended up conceding a corner. To have so many defensive-minded players, to lose a goal like that was criminal, really."
Agger, who missed Monday's 2-2 draw with Swansea due to a knock, was replaced by Jose Enrique on 57 minutes.
Rodgers continued: "He's had the problem with his side. We needed him to play, really. He hadn't trained all week and felt a bit of pain in the game, so we decided to take him off, try and be a bit more offensive and see if we could get 30 minutes or so out of Enrique.
"It's not ideal to have to play that [four centre-backs]. If it's something where we don't have players back fit and recovered, we may have to look at a different system that allows it to work.
"But we'll just accept that today we're not happy and we'll look forward to Wednesday night."
In addition to Glen Johnson and Aly Cissokho, Liverpool were also without the injured Philippe Coutinho, who was ruled out until towards the end of October due to a shoulder injury.
"We've been unfortunate to lose a number of injured players all at the same time," said Rodgers. "And when you bring out the likes of Glen Johnson and Coutinho and you haven't got Suarez in your team, then it can make a big difference.
"But we have what we have and the players have been brilliant. Today hurts, because we haven't tasted defeat for such a long time. I'm still very optimistic for the season. We've had good wins and we've drawn.
"Obviously the defeat today was hard to swallow, but our optimism is very much intact and we feel we can have a really good season."
Meanwhile, journalists asked Rodgers about the return of Luis Suarez from suspension.
The striker completed his ban against the Saints and will now become available for selection.
"I think that's a positive from today; the fact that he is back now, the ban has finished and he's available from next week," said Rodgers.
"But I can't underestimate how well the players have done. It's worth mentioning that this is our first defeat since March, where we lost against Southampton. So we've had two poor performances against them and it's cost us.
"In that period the players have been brilliant. Today was one of those days when we were right off it.
"Sometimes in these games it's players like him [Suarez], who can make the difference. It's going to be great to have him back."
On Suarez's fitness, Rodgers added: "I think he's in a good condition and he's been playing games, both behind closed doors and ones that have been organised for him. He's been doing a lot of specific work with the conditioning teams.
"He's obviously not going to be 100 per cent, when you come into these sorts of cup games and these games that are at a greater intensity.
"But he's a worker and he's a fighter and his condition is good. He's in a good place. He just needs to get games to bring him right up to full speed."