GLASGOW - Celtic manager Ronny Deila slammed his side's mental approach as the Scottish champions slipped to a surprise 2-2 draw against Kilmarnock at Rugby Park on Wednesday.
The Hoops twice let a lead slip through their fingers as their winning start to the Scottish Premiership campaign came to an abrupt halt.
Leigh Griffiths put Celtic ahead in the second minute and the Hoops missed a host of chances before Josh Magennis levelled matters against the run of play in the 35th minute.
Nir Bitton's sensational strike 10 minutes into the second half looked to have given Celtic the win but Kallum Higginbotham's 87th-minute chipped penalty helped bottom of the table Killie deny the defending champions their third consecutive victory.
The result saw Celtic replaced at the top of the table by newly-promoted Hearts, who made it three wins out of three following their 2-0 defeat of Motherwell thanks to a Gavin Reilly penalty and a Billy King strike.
Celtic boss Deila was dismayed by his team's lapses at both ends of the pitch.
"We had a lot of chances today and we were not clinical enough in our finishing. We also gave away way too many chances," a disappointed Deila said. "There were more goal chances against us today than we've had for 10 matches, so that was disappointing.
"Credit to Kilmarnock who put us under pressure but we also need to do things differently and be much more disciplined in what we do.
"We should have been two or three ahead going into the break but we didn't score goals and that's the most important thing in football." Celtic set the record for fewest league goals conceded in a season since 1919 when they let in a measly 17 goals during the last campaign.
Despite Kilmarnock's goals being the first his side had conceded in the league since April 22, Deila knows Celtic will need to improve ahead of next week's crucial Champions League qualifier against Swedish side Malmo.
"We won't get away with defending like that next week against Malmo but we have defended very well this year. We had the best record in Scottish football so we can defend," the Celtic manager said.
"We have good players, but it's disappointing that we are lacking discipline. We did it in the second half against Partick Thistle and we did the same today. In the end we got punished.
"We need to be 100 percent switched on, defensively and offensively in every game. I expect us to be back on track again on Saturday.
"It's always tough. We took one point - we wanted three but we didn't deserve any more." Southampton have been linked with a move for Hoops defender Virgil van Dijk, but Deila denies the Dutchman will be going anywhere before Celtic's Champions League fate is decided.
"We want to keep him. We don't need to sell him and he's going to stay here - for the qualifiers anyway," Deila added.