WHAT is it with Dundee, are they under a curse?

No-one needed to see the colour of the scarf to identify the fans of the beaten team on Tayside last night. They were the ones with their faces tripping them, utterly fed up that they had been brought down yet again by the Arabs. Around the city they reckon John Brown was brought in as interim manager with this William Hill Scottish Cup quarter-final in mind. Now that it's over and lost, and relegation also seems inevitable, some will think the dismissal of Barry Smith more futile than ever.

Brown fumed about a throw-in going United's way in the first half of this ugly mess of a match. He was right to highlight that Gary Mackay-Steven had run the ball out of play before bringing it back in and being tripped to get a free-kick. Barry Douglas swung in a fine delivery and Brian McLean rose to bullet a header into the net.

Brown admitted he felt "pretty bitter" about assistant referee Andrew McWilliam calling the decision for the wrong team: "It was a clear throw-in but it wasn't given and ultimately resulted in the free-kick leading to the goal. I don't need to talk about how to defend it because it shouldn't have happened. An official has cost this football club a replay and the chance to get to a semi-final. I spoke to the referee supervisor Bob Valentine and he said the ball was out. It's human error but it's a sore one to take. I was 10 yards away, it was right there, so how he can't see it - the only person who couldn't see it was the linesman who is five yards away. I can't believe it."

Jim McAlister, despite equalising within minutes, broadened Dundee's protest: "You look over the course of the season and wonder how many times officials are going to cost us."

Frankly, all of that sounded pretty hollow. A quarter-final is not won or lost by who gets a throw-in after 11 minutes. Dundee's defenders will hope Brown continues to fix on that mistake by the assistant referee rather than the ones they made when coping dreadfully with the free-kick which followed. Lewis Toshney was especially culpable as the man who was on McLean but let him get away to score.

Some things seem never to change in this fixture. That is three consecutive wins for United this season – four if you include a pre-season friendly – and Dundee have not beaten them at all since 2004, or in the Scottish Cup since 1956. They were not outclassed or outfought here but such is the lack of quality in their squad they huffed and puffed for much of the match, doing little on the occasions they had United pinned back.

Brown was the pantomime villain, mocked by the United supporters as he walked in and out of the tunnel near them, but his team actually ran United a lot closer than Smith's had in two 3-0 defeats earlier in the season.

Dundee responded well to going behind and had some joy at unsettling United. They were rewarded with a nicely executed equaliser. Steven Milne flicked the ball to John Baird and he held it up before laying off a pass for McAlister to bury a finish into the corner. Baird then had a couple of chances of his own, the second forcing Radoslaw Cierzniak into a sharp reaction save with his legs. United looked jittery.

There is quality in the United squad that Dundee can only envy, though, and they prevailed even without Johnny Russell who had failed a late fitness test. They calmed themselves by regaining the lead from a clinical counterattack. Willo Flood released Stuart Armstrong and he powered confidently through midfield before slipping a deft pass to put Mackay-Steven in on Rab Douglas at the edge of the box. His instant low shot went through the veteran goalkeeper, who should have done better. It was pretty harsh of referee Iain Brines to book Mackay-Steven for putting his finger to his lips to shoosh the Dundee supporters, but he still could not get the smile off his face.

Would Gary Harkins have made a difference? Dundee's talented forward was ineligible and they felt the absence more keenly than United felt Russell's. There was no hint of invention without him. The closest they came to goal in a desperately drab second half was when McLean glanced a header back to Cierzniak without realising his goalkeeper had come off his line. The ball ran towards goal, but wide. Dundee ran themselves into the ground and out of steam.

"It was a typical cup tie and derby, not a lot of quality in the game, not a lot of passing," said Jackie McNamara after his first as United's manager. "I left Partick Thistle in a cup final, in the Ramsdens Cup, so hopefully we can get to the Scottish Cup final to make up for it."

Another cup final for United, maybe winning it for the second time in four years? Yeah, that's all Dundee fans need right now.