Callum Davidson was disappointed with the decision that resulted in Melker Hallberg’s sending off.
The Swedish midfielder, already on a yellow for a first half foul on Tony Watt, picked up another early in the second half.
Despite the numerical disadvantage, Saints battled superbly well to pick up a hard-earned point against Dundee United at McDiarmid Park.
“I’m not happy with the sending off,” Perth boss Davidson said. “I didn’t think there was anything in it and I still don’t after watching it back.
“If you are going to book players for what Melker did then every player on the pitch is going to get booked.
“For me it is really soft and another disappointing decision against us.
“It could have cost us the three points and it means we lose an important player for the next game.
“He has been fantastic since he signed and it is important he plays for us.
“I was told it was a tug and then told it was an arm around the neck. I still can’t see any of those.”
Saints had hit the underside of the crossbar through Ali Crawford in the opening half but were required to dig in for the final 35 minutes.
“I thought it was an entertaining game in the first half and we had the best chance,” Davidson added.
“It fell to Ali Crawford and normally he sticks them away.
“It was a tight game and in the second half I thought we were super. We really limited Dundee United to just a few chances when we were down to 10 men.
“I was really pleased with the boys’ attitude.
“There was a lot of positives and I have been delighted with the attitude of the boys. There is no lack of spirit and desire.”