United manager Craig Levein admits he has marvelled at the way Scott Robertson has taken to life in the Scottish Premier League.

The 23-year-old, who scored in the 2-0 win over Airdrie to move United into the quarter-finals of the Co-operative Insurance Cup, signed for United from city rivals Dundee in the summer, ending a five-year chase by Levein for his signature.

He first tried to capture the player when he was at Dundee but he finally got his man in June, with Robertson ending his 10-year association with the Dark Blues.

Levein has watched him improve almost week on week so far and praised him for the way he has coped with the pressure of crossing the city.

He said: "Scott has been excellent for us since he came here.

"He's settled in straight away, although I'd expect that because he's a Dundee boy.

"But coming across the road, over the great divide, is always going to be a challenge but he's come on in leaps and bounds even in the short time we've had him.

"It's great for him to get a goal. He is playing in a much more attacking position than he was in the first few weeks of the season so he'll benefit from that.

"He's building a good relationship with Morgaro Gomis in midfield and there's loads of improvement still to come from the pair of them."

Robertson's goal in the cup added to David Goodwillie's 32nd-minute strike.

United struggled at the start of last season but have now recorded back-to-back wins and their manager feels their season is now really kicking off.

"I'm delighted with the victory, I thought we played really well, showed a lot of patience and had good quality in the final third," said Levein.

"The fans were really good as well because they realised we had to be patient, pass the ball and that was the best way to go about the game.

"It's the first time we've won back-to-back games for a bit and now we want to make it three against Hearts on Saturday."

Airdrie boss Kenny Black admitted his side were second best and lamented their failure to hit the heights reached against Hearts in the last round.

The Diamonds looked set to equalise when the game was at 1-0 but Lukasz Zaluska denied them with a stunning save.

Black said: "We needed to produce the kind of performance we did against Hearts and I don't think we reached it.

"It might have been interesting if their goalkeeper hadn't made that save and we got the equaliser but it wasn't to be.

"I thought it was in, I was just about to jump up to celebrate but what a top-class save it was.

"But over the 90 minutes United were the better team so we've got no complaints."