Dundee do not get six minutes added on when they need it like Celtic do, suggested Jim McIntyre after his side lost to a last-gasp Odsonne Edouard goal.
The Dens Park side had held the league leaders until the Frenchman's goal on 96 minutes.
But McIntyre felt the extra time was unwarranted.
"We never seem to get six minutes added on when we are looking for it. I found it strange to say the least," he said.
"It was a real surprise.
"I asked the fourth official, John Beaton, and he explain the referee felt there were three head knocks as well as the substitutes.
"I don't want to make too much of that. In the last two minutes we had a great opportunity and we have to do better. Celtic break from that and score."
Dundee had defended valiantly, but after Martin Woods' deflected shot was collected by former Dens Park favourite Scott Bain, Celtic went up the other end with Edouard playing a one-two with Forrest and tapping home in a crowded six-yard box.
It leaves Dundee just a point above bottom side St Mirren but the Buddies could overtake Jim McIntyre's team by winning their game in hand against St Johnstone, with Hamilton Academical six points ahead of the Dens Park outfit.
McIntyre told BBC Scotland: "We just have to be better in those situations and that's why we are where we are. We've given away too many points here because we've not shown our ruthlessness."