After going down 1-0 to Swansea City, Jurgen Klopp said Liverpool's sensational triumph over Manchester City last time out felt "like half a year ago".
Liverpool became the first team to defeat Pep Guardiola's side in the Premier League this season with a 4-3 victory at Anfield on January 14, but they were brought back down to earth by Swansea on Monday.
Alfie Mawson's first-half strike proved the difference, with a "frustrated" Klopp unhappy with the application of his players at the Liberty Stadium.
"Last weekend [against City] feels like it was half a year ago, it's not what I'm interested in," he told Sky Sports.
"We're frustrated, I'm frustrated, I'm angry because of what we did today. We have to get the points, we have to learn from it. The boys did better in the last few weeks but that does not help us tonight.
"We lost the game in the first half. Not only because we conceded the goal - It can happen like this - but because we didn't keep the positions we wanted to be in.
"We wanted to do it differently but it didn't happen on the pitch for us. At half-time we said OK, maybe we can start doing what we wanted to do at the beginning.
"But because of the first-half we weren't that secure or confident in what we were doing."
Liverpool went close to earning a dramatic 94th-minute equaliser when Roberto Firmino's header struck the upright and Mawson stopped Adam Lallana turning home the rebound.
"We had moments where we looked like we could score. The clearest chance we had was in the last second more or less, I don't know how the ball is not in," said Klopp.
"A point would've been OK but not what we wanted, so wouldn't have made the game any better to be honest.
"We had to play football and we had plenty of opportunities after the restart, but in the end it wasn't good enough."
The result ended Liverpool's 18-game unbeaten run in all competitions and left them fourth in the Premier League.
|CA dismisses spot-fixing claims|
|WATCH: Will Ferrell leads chants with LAFC fans|
|MLS Review: Galaxy on track for play-offs as Timbers, DC clinch spots|
|Elliott secures win at Hollywood Casino 400|
|Thunder´s Westbrook makes season debut against Kings|
|Saints beat Ravens after Tucker misses extra point|
|Rondo, Paul and Ingram banned after Lakers-Rockets fight|
|Saints QB Brees reaches another historic milestone|
|Biglia: VAR should have checked Nainggolan tackle|
|Gattuso not blaming Donnarumma for derby defeat|
|Seventh in Mexico will secure Hamilton´s fifth world title|
|Rooney fires DC United into MLS play-offs|
|Alonso slams ´amateur´ F1 rivals after latest crash|
|Spalletti fears lengthy Nainggolan absence|
|To the Max! Verstappen destroyed shoe fending off Hamilton|
|Icardi delight after Donnarumma error gives him another derby winner for Inter|
|Guardiola: Versatility the key for Stones|
|Vettel frustrated as mistakes continue to hamper title challenge|
|ECB refutes spot-fixing claims against England players|
|I thought we would do better - Hamilton queries Mercedes strategy|
|Inter 1 AC Milan 0: Icardi settles derby with dramatic late winner|
|Hamilton denied title party as Raikkonen wins in Austin|
|Patriots RB Michel out against Bears with gruesome knee injury|
|Kohli hails Rohit partnership after comprehensive India victory|
|Silva downplays his role after Everton super subs seal victory|
|Injured Bairstow out of final white-ball matches in Sri Lanka|
|Pliskova feeling confident after impressive start in Singapore|
|Big-hitting Imrul rescues Bangladesh in opening ODI|
|Leinster suffer late defeat at Toulouse, Newcastle snatch dramatic victory|
|Chargers pip Titans to dramatic London win|
|Everton 2 Crystal Palace 0: Substitutes Calvert-Lewin and Tosun clip Eagles´ wings|
|Thunderstorms push Andalucia Valderrama Masters into reserve day|
|Edmund masters Monfils to claim maiden singles title|
|Kohli and Rohit fire India to comprehensive ODI win|
|Manchester United didn´t play - David Luiz blasts Mourinho tactics|
|Svitolina out to silence ´haters´ in Singapore|
|Emre Can facing surgery on thyroid problem|
|Tsitsipas claims maiden ATP crown in Stockholm|
|Mariners boss Mulvey knows nothing of Bolt contract offer|
|WATCH: Vinicius Junior scores free-kick - then sees red!|
|Gronkowski ruled out of Bears clash|
|Khachanov enjoys home comforts with comprehensive Kremlin Cup win|
|Isner wants Wimbledon tie-break rule named after him|
|Hummels lauds ´outstanding´ Lewandowski|
|Liverpool´s defensive improvement no accident – Gomez|
|Pliskova overpowers defending champion Wozniacki in Singapore|
|Marquez dislocates shoulder celebrating MotoGP title|
|Henry taking positives from opening Monaco defeat|
|A-League Review: Mariners held as Bolt considers move|
|Dominant Svitolina ends Kvitova hoodoo in Singapore|
|Pereira warns Juventus to expect ´pumped up´ Manchester United|
|D´Antoni backs NBA to ´sort out´ Lakers-Rockets brawl|
|Mixed feelings for champion Marquez after Dovizioso crash|
|Bolt offered contract by Central Coast Mariners|
|Anthony accuses Rondo of spitting after Lakers-Rockets brawl|
|Martial insists he has good relationship with Mourinho|
|Bautista to replace Lorenzo at Phillip Island|
|Emery wanted Lacazette at Paris Saint-Germain|
|Wallabies centre Hodge suffers fractured ankle|
|Koepka claims top ranking with CJ Cup win|
|Dramatic Dovizioso crash gifts Marquez MotoGP title in Japan|
|LeBron´s home debut ends in defeat, Walker makes NBA history|
|Rondo, Ingram and Paul exchange punches in Lakers-Rockets clash|
|Dodgers to face Red Sox in World Series after beating Brewers|
|Valverde doesn´t care about extending Barca contract|
|Qualifying speed a ´positive surprise´ for Ferrari´s Vettel|
|I was in a different headspace – Hamilton revels in Austin pole|
|Barcelona can cope without Messi – Pique|
|Allegri: Juventus abandoned Genoa clash|
|Sale: Hospital visit was because of belly button ring|