Celtic lost 3-1 to Molde in the Europa League on Thursday, and Deila was very disappointed with his side's display.
The Bhoys were far from their best in Norway, and Deila was left frustrated after the tactical advice he gave to his players fell on deaf ears.
“We talked before about playing with balance and we had to come around on the side and get crosses but we didn’t manage to do that," he explained. "We were not switched on enough.
“Everything was too slow. I expected much better and I’m very disappointed, of course.”
Celtic's defeat leaves their chances of qualifying from their Europa League group looking slim, with the Scottish Premiership champions failing to win any of their first three matches in the competition.
The Bhoys have been handed a tough group, but they would have expected to make a better start than they have, and Deila is starting to come under pressure.
Although Celtic have made a good start to their domestic campaign, simply winning the domestic title isn't enough for any manager at Parkhead.
Celtic's failures in Europe over Deila's two years in charge have not reflected well on him, and some sections of the crowd are now actively calling for him to lose his job.