United crash out of the cup agains Inverness CT in a lackluster display.

The breakthrough came when Duncan took possession of the ball 25 yards from goal before rifling a brilliant drive into the top right-hand corner of Derek Stillie's goal.

Rory McAllister should have doubled the Highlanders' advantage but sent a header over from six yards out, while Caley Thistle goalkeeper Michael Fraser did well to parry a powerful injury-time shot from Barry Robson.

Following a tight opening to the match, it looked like it would take something special to break the deadlock and that memorable moment arrived in the 16th minute.

When the ball broke to Duncan, there looked to be little on, until the midfielder thumped a searing shot past Stillie to hand Inverness the lead.

Caley Thistle then immediately took control against a United side who were struggling to get the ball out of their own half, and the Highlanders should have deservedly doubled their lead 12 minutes later.

Roy McBain was the catalyst courtesy of a driving run which took him from one side of the pitch to the other, and eventually the former Ross County player knocked the ball back from the left wing to Duncan.

The Caley Thistle goalscorer whipped a delightful pass out to Barry Wilson on the right and he in turn immediately delivered an excellent cross into the United penalty area.

The ball was met by McAllister only six yards from goal, but the young forward directed his header over the crossbar when he simply had to hit the target.

Eight minutes before the break the visitors finally ventured forward again and David Robertson spun to hook an effort wide after Lee Wilkie's initial shot had been blocked.

Christian Kalvenes then tested Fraser with a 30-yard-drive which the goalkeeper gathered at the second attempt and United had some renewed hope heading into the second period.

The visitors started in positive fashion following the interval and when Mark Kerr's deflected shot was not claimed by Fraser in a congested penalty area, Robertson headed into an unguarded goal, but the effort was correctly ruled out for offside and United remained behind.

The home side responded with a brilliant run from Wilson which saw him beat a host of United players before knocking a cut-back into the path of the on-rushing McAllister, who rolled a disappointing effort wide.

Fraser then did well to save a half-volley from Kerr, while Ross Tokely should have added a second for Inverness when an outrageous body swerve took the right-back past three United defenders.

With only Stillie to beat, Tokely rolled the past the wrong side of the near post and was almost made to pay for that miss late on.

A typical surge from Robson gave the United captain room to blast in a shot from 18 yards, but Fraser produced a brilliant parry, as it was Inverness who moved into the next round.