Celtic lost to St Johnstone in a surprise result in the SPL.
Celtic manager Ronny Deila has admitted there are no excuses for his side's loss to St Johnstone.
The Norwegian said that his side simply did not play well enough, but was determined that his side get back to winning ways.
He made the comments in his post-match press conference, put out by the club's official Twitter feed:
RD: "It’s not about finding excuses. The performance wasn’t good enough." (MH)— Celtic Football Club (@celticfc) March 4, 2015
RD: "We have had a hard programme with important matches and we had a big setback tonight." (MH)— Celtic Football Club (@celticfc) March 4, 2015
RD: "I am disappointed but we have to bounce back on Sunday and find a positive from this in the end." (MH)— Celtic Football Club (@celticfc) March 4, 2015
It was Celtic's first defeat of 2015, and brings to an end an impressive run domestically, unbeaten in 11 games previous to the clash at Parkhead.
St Johnstone won through a goal from Danny Swanson, scored from 25-yards out.
Despite the defeat, Celtic have a six point lead at the top of the SPL, with this their game in hand which could have extended their advantage over Aberdeen to nine.
Celtic's next game is against Dundee United, a quarter-final of the Scottish Cup, one of three consecutive games they will play against the club in different competitions.
The club are still on for a treble, but it is their second loss in three games, losing to Inter Milan in the Europa League a week ago.