IT was a case of what might have been for Rangers yesterday.

After another hard week for Ally McCoist, the players, and the fans, few people would have expected them to run Dundee United close in their Scottish Cup semi-final at Ibrox.

The 3-1 win for Jackie McNamara's side looks comfortable on paper but Rangers will be kicking themselves, with four big mistakes ultimately costing them the tie and a place in the final. It was a much-improved performance, probably their best of the season, from Rangers, but it didn't prove enough on the day.

I thought United played well below what they are capable of but they did the most important thing and took their chances, which Rangers didn't do.

I have said for months that you can't just lift and drop your performances all the time. You can have a couple of games a season where you say: "We weren't at our best but we won." That is fine over a course of a campaign.

But how many times have we said that about Rangers this year? A dozen, 15, 20? When you are below par that often, you can't just flick a switch and turn it on, and we saw that yesterday. When it comes to facing better-quality teams, you have to take your chances and defend properly. Rangers didn't do that and were punished for it.

Dean Shiels and Jon Daly should have scored and then they didn't defend properly for the first goal.Steve Simonsen made a real howler for the third goal when they were chasing the game going into the last few minutes.

Rangers did a lot of things right. I would say United's front four were quiet but the Ibrox side can't make the mistakes they did and get away with it. It happened against Raith Rovers last week and it happened again yesterday. In the big moments that define games, Rangers were found wanting, and it cost them a place in the final.

It has been a mixed season for Rangers, even though they have won League One comfortably. If they had won the Ramsdens Cup and won the game yesterday, it would have been a really good season for them.

From United's point of view, and Jackie said it after the game, they don't care about the performance, it was all about the result. Jackie will know they weren't at their best and they will have to play better but there was a lot of pressure on them yesterday.

They are inexperienced at this level and it was a real test of how the younger players would handle the occasion. I think it will have brought them on leaps and bounds. They coped with the big-game atmosphere and did enough to make sure they got through the tie. They weren't at their best but they can be pleased with the result and look forward to the final now.

They will find out who they will face at Celtic Park this afternoon when Aberdeen play St Johnstone at Ibrox. I have said all week nobody would begrudge Tommy Wright's side a place in the final and I wouldn't mind seeing them get there.

But when you look at it, Aberdeen will have to be the favourites and they will expect to get through today.

They have already won the League Cup and that will stand them in good stead: they have already handled the pressure and know that they can win big games.

I don't think Aberdeen are a brilliant team but they are playing with confidence, they have got a good team spirit and they are winning games. I don't think they will romp it but I think they will do enough to set up a New Firm final at Parkhead.