Dundee boss Paul Hartley wished his side had scored earlier to heap pressure on Celtic.
With the clock ticking down in Wednesday night’s match, the Hoops looked to be cruising to a victory thanks to a first-half goal by former Dundee United star Gary Mackay-Steven and a second-half wonder free-kick by Virgil Van Dijk.
However, Dundee’s Jim McAlister popped up with a counter in the 88th minute but the Dark Blues just could not snatch an equaliser.
Hartley said: “I thought we were good. We just lacked a little cutting edge.
“If we’d scored the goal 10 or 15 minutes previously we’d have had them worried.
“Two set-pieces have done us in. I thought we worked well, we were well organised and there was good discipline to our performance.
“We were playing a good team. Celtic have quality throughout their team.”
Hartley though admitted he was left baffled by some “bizarre” decisions by referee Calum Murray, especially just prior to Celtic’s first goal with the official playing an advantage before awarding the original free-kick to the Hoops.
The build-up to the game had, of course, been overshadowed by the Glasgow side’s controversial Scottish Cup semi-final defeat against Inverness and the furore over the officials’ performance.
This time though it was Dundee and Hartley who were left unhappy by a referee’s decisions.
When asked if he felt aggrieved by the free-kick in the lead-up to the first goal, Hartley said: “He brought it back because Celtic gave the ball away.
“Those decisions happen throughout a game. There were a couple of decisions that we weren’t happy with. Some decisions were quite bizarre.
“I think they (officials) are always under pressure but what’s happened in the last couple of days meant the scrutiny was always going to be on them all the time.
“They can’t do that. We understand they have a tough job in high-pressure games.
“We had one in the first half and the referee gave offside and the linesman didn’t.
“He made a mistake and admitted that to me at half-time.”