Manager Paul Hartley felt referee Bobby Madden had a hand in denying Dundee victory over St Johnstone at Dens Park.
David Clarkson was refused a sixth-minute penalty after clashing with goalkeeper Alan Mannus and was booked for his troubles in the 1-1 draw.
Hartley told BBC Scotland he thought it was "an incredible decision".
"We should have a stonewall penalty," he added. "That might have changed the game if they go down to 10 men and we have the opportunity to score."
Clarkson went on to find the net from close range after 40 minutes, only for on-loan Dundee United striker Brian Graham to equalise with a 53rd-minute spot-kick.
"David is a honest player, he came in at half time and said he's been caught by the goalkeeper," explained Hartley.
"I don't want to see players sent off but I thought it was the wrong decision.
"I had no complaints about their penalty, though, and it kind of spooked us as we just didn't get going again after that.
"I didn't say anything to the referee at half-time or full-time. There is no point because you are just full of emotion.
"In the second half we weren't as good. In saying that we're still on a good run of form. We had some very good performances and there is a lot to be positive about as far as we're concerned."
Dundee had another penalty claim when Greg Stewart toppled in the second half, with Hartley adding: "It was one of those days for us".
Clarkson's goal was his sixth in six games and Hartley is delighted with the impact the former Motherwell striker has made.
"He's a man on form," he enthused. "Everything he touches seems to be going into the back of the net - and long may it continue.
"He's been absolutely terrific for us, with his hold up play and experience."