Inverness manager Terry Butcher struggled to fathom where it all went wrong during the 1-0 defeat to Celtic.
Butcher saw his side dominate the opening stages before being overrun after the break when Paddy McCourt smashed in the only goal.
"I'm bitterly disappointed with the second 45 minutes because the first was very good," Butcher said.
"We were very pleased at half-time and wanted more of that and we didn't get anything.
"It was like I made 10 substitutions. Ryan Esson was magnificent and kept us in the game, although we didn't deserve to be in the game at that point because Celtic dominated possession in the second half.
"I don't know where the second half came from. We will analyse it to see where it all went wrong."