Celtic manager Neil Lennon was left angered after his side's 4-2 defeat against Rangers at Ibrox.
The Hoops had led 2-1 at half-time, but Rangers fought back to claim the three points in the first Old Firm derby of the season.
"I am angry, full stop, with our overall performance. I wouldn't like to question their character but I had to ask that after the game," said Lennon.
"We didn't compete and it was almost as if the players went out for the second half thinking the game was already won."
The defeat leaves Celtic in second place in the SPL table, four points behind their Glaswegian rivals.
