Celtic manager Brendan Rodgers conceded his side have made a disappointing start to the season after they slipped to a second defeat in six games, losing 2-1 to Kilmarnock.
Leigh Griffiths gave the champions the lead after 34 minutes at Rugby Park but, after Chris Burke's equaliser half an hour later, Celtic were undone by as stoppage-time winner from Stuart Findlay.
The result leaves the Bhoys fifth in the table after six games, six points behind league leaders Hearts, who beat Rodgers' men 1-0 earlier in the season.
"It hasn't been a great start to the campaign but we have to accept that," Rodgers told a post-match news conference.
"We're the only ones who can make it better by playing better and getting more consistent results.
"It's been very bitty but we have to go away and work and see where we can be better."
Celtic meet St Johnstone in the League Cup on Wednesday before entertaining Aberdeen at Celtic Park on Saturday, and Rodgers believes fatigue from Thursday night's 1-0 victory over Rosenborg in the Europa League may have been a factor.
"I take responsibility," he added.
"We made the changes to try and get that energy and brightness and sharpness that may not be there if you've played late on a Thursday night.
"I'd have been disappointed to draw the game but to actually lose is bitterly disappointing."
|Messi absence big blow for Barca as Icardi talks up Inter|
|´You can´t cry, that´s true´ – Ronaldo responds to Isco|
|Bartomeu: Barca still competitive without Messi|
|Bills RB McCoy remains in concussion protocol|
|Raiders place Marshawn Lynch on IR|
|Emery calm over title talk after another Arsenal win|
|Green: Warriors have to clean up defensively|
|Mariners say Bolt talks ongoing amid reports contract offer was rejected|
|Proud captain Ozil revels in Arsenal´s ´sexy football´|
|Puel angry over Holding handball|
|Cilic breezes through in Basel, Anderson fights back|
|Ingram: Four-game ban better than we expected|
|Raiders send Cooper to Cowboys for first-round pick|
|Arsenal 3 Leicester City 1: Outstanding Ozil inspires comeback win|
|World Series 2018: Three reasons why the Dodgers will win|
|Yarmolenko out for six months after Achilles surgery|
|World Series 2018: Three reasons why the Red Sox will win|
|Ozil eclipses Klinsmann to become Premier League´s most prolific German|
|Allegri expecting Old Trafford battle against Mourinho´s United|
|Bertens feared she did not belong in Kerber clash|
|Returning Ronaldo expecting ´tough´ game against Manchester United|
|Cristiano Ronaldo confident of clearing his name amid rape allegation|
|Osaka looking to learn from losing start in Singapore|
|Kovac expects tough test against AEK Athens|
|Whyte gives Chisora deadline over rematch|
|Spartak Moscow sack Massimo Carrera|
|Atletico Madrid confirm fresh injury issue for Gimenez|
|Dolberg extends Ajax contract after Real Madrid links|
|Ronaldo an example for Lukaku to follow|
|Bertens battles back to blast past Kerber|
|Ramos apologises for training ground fracas|
|Raikkonen should take heed of Alonso misfortune as F1 career winds down|
|Guardiola wants Manchester City fans to push team to Champions League glory|
|Isco not interested in departed Ronaldo - he didn´t want to be here|
|World Series 2018: Three storylines to watch in Red Sox-Dodgers|
|Neymar focus bad for football - PSG´s Maxwell|
|Marco Ianni charged by FA over Jose Mourinho touchline row|
|Stephens sees off Osaka in see-saw Singapore battle|
|I´m happy at Manchester United - Mourinho dismisses Real Madrid reports|
|Semenya and Asher-Smith head IAAF Female World Athlete of the Year shortlist|
|Mandzukic to miss Manchester United trip|
|I turned down Manchester United to return to Juventus - Bonucci|
|Sanchez out of Manchester United´s clash with Juventus|
|Australia make Short work of run chase in T20 win|
|Brotherly g-love! Tommy Fury follows Tyson into the pros|
|Ozil´s international retirement can help Arsenal - Emery|
|If you sack Lopetegui, you have to sack us all – Isco|
|Lopetegui defiant amid Real Madrid sack reports|
|Sri Lanka spinner Herath to retire after Galle Test|
|Ronaldo returns for Old Trafford welcome amid disquieting noise|
|Garcia claims third Andalucia Valderrama Masters title|
|Ex-England international Waldrom retires|
|´Massive personality´ Hart can lift Burnley, says Kompany|
|Liverpool felt wrath of ´emotional´ Klopp, says Shaqiri|
|Reid: Jenkins capitalised on Kaepernick movement|
|Manchester United v Juventus: Ronaldo out to end dismal scoring record against Mourinho|
|Injured Ribery to miss Bayern´s clash with AEK|
|Wilshere would have stayed at Arsenal under Wenger|
|Mahomes stars again as Chiefs crush Bengals|
|Bolt must accept ´much less´ to join Mariners, says A-League chief|
|Klopp compares Liverpool to dog without favourite toy|
|Young leads Hawks to first win, Thunder fall in Westbrook´s return|
|Spalletti hits out at physical Milan – I had three players asking to be replaced|
|Cowboys, Ravens lose after missed kicks in final seconds|
|Hernangomez secures Nuggets´ win over Warriors with last-second block|
|Hasler returns to Manly on three-year deal|
|Sarri: Chelsea fans must respect Mourinho|
|Ronaldo learnt from Scholes – Pjanic praises Juventus star|
|CA dismisses spot-fixing claims|
|WATCH: Will Ferrell leads chants with LAFC fans|