Ange Postecoglou said his green and white rotation game "probably" didn't help after Celtic crashed to just their second defeat of the season against Rangers.
The Parkhead boss watched his champions crash to an error–strewn 3-0 defeat at the home of their rivals, the heaviest domestically of his reign to date. Todd Cantwell got the scoring going at Ibrox and John Souttar headed home another for Rangers before half-time. A catalogue of mistakes then allowed Fashion Sakala to put the game to bed and ensure Celtic can't make a record-breaking Premiership total of 106 points, sitting on 95 points with three games to go.
Speaking to Sky Sports, Postecoglou said: "We are disappointed. We didn't perform at the levels we needed to today. There were probably a few critical moments where we should have got ourselves back into it and we didn't.
"The second half we were a little desperate in our play and didn't play our football. Credit to Rangers, you are facing a difficult opponent at their venue.
" The amount of changes I made probably didn't help in terms of lacking a bit of sharpness, at the end of the day we just weren't good enough.
"Every game is a challenge and every game is an opportunity, we have had to work awfully hard to make sure we maintain our levels. We didn't get to them today."