Dundee United boss Robbie Neilson claimed referee Willie Collum allowed his side's 2-1 William Hill Scottish Cup last-16 win over St Mirren to turn into a kicking match by not sending off Saints skipper Paul McGinn.

The Championship side were leading in Paisley through first-half goals from Pavol Safranko and Nicky Clark when McGinn crashed into former Saints midfielder Cammy Smith.

Neilson was furious that Collum only produced a yellow card and his fury was compounded in the 62nd minute when the official did show a red to United's Calum Butcher for a high challenge on Ryan Flynn.

Striker Duckens Nazon's first goal for St Mirren, a deflected strike in the 77th minute, reduced the deficit, but the 10-man visitors held out under mounting pressure to go into Monday night's draw.

Neilson said: "I thought it was a disgrace.

"He saw it, the fourth official saw and watch it on the TV tonight.

"The referee's decision not send Paul McGinn off made it a fight and a battle, everyone starts kicking each other and he tried to calm it down by sending one of my players off.

"When you see the picture of it, the two of them have their legs up and he's probably seen my player going in and he's thought, 'I need to calm this down', because as soon as he doesn't send McGinn off, everything just escalates and they think they can get away with anything.

"I don't really want to come and speak about referees because we are trying to calm it down, but it went from a really god performance from us to a physical game where it is just kicking each other and he decides to send someone off and it just a lottery after that.

"Then it was backs to the wall, so I was disappointed with that side.

"But to come to a Premiership club and dominate for a considerable 55 minutes was good."

St Mirren had come back from 2-0 down to beat Alloa 3-2 in the previous round, but manager Oran Kearney had warned his players that they would not be able to do that against United.

He said: "We left ourselves with too much to do.

"I told the players in my team talk we couldn't have another Roy of the Rovers like the last round.

"Sadly for us that is how it panned out without the end prouct this time.

"We possibly could have got a replay or more out of it on chances created.

"But you can't keep expecting to win a game in Roy of the Rovers fashion."