Robertson nudges the ball beyond McGregor for United's late winner
By Andy Campbell
Dundee United claimed a place in the semi-finals of the Scottish Cup after denying Rangers the chance to win the domestic treble.
Kyle Lafferty handled in the Rangers box in the first-half but escaped the award of a penalty against his side.
United were dominant for most of the game and David Goodwillie had the ball in the net, only to be flagged offside.
However, David Robertson's last-minute effort did count to book the Tangerines a place in the last four.
Peter Houston's side will now take on Raith Rovers at Hampden for a place in the final.
United started the quarter-final replay on the front foot and Jon Daly stung the palms of goalkeeper Allan McGregor with a fierce early drive.
John Fleck, one of seven changes in the Rangers starting line-up from Sunday's Co-operative Insurance Cup final win, drove at the home defence and had a shot blocked by Sean Dillon before Mihael Kovacevic's audacious dipping volley drifted just wide of McGregor's right-hand post.
Rangers' Steven Naismith was inches away from scoring an own goal when his clearance crept across the face of goal and out.
Craig Conway's 31st-minute free-kick was headed towards goal by Daly and Lafferty's outstretched hand diverted the ball over the bar.
However, despite strenuous penalty appeals from the United players, referee Dougie McDonald awarded a corner to the home side and booked Garry Kenneth for dissent towards the assistant referee.
Kovacevic was injured whilst tackling Fleck in first-half injury time and the full-back was replaced by Keith Watson before the interval.
The Scottish Premier League leaders, minus Kevin Thomson after a last-minute appeal against a suspension was turned down by the Scottish FA, looked increasingly disjointed after the break and struggled to put pressure on the home goal.
Conway's attempted shot looked to be heading wide but Robertson flicked the ball awkwardly towards goal and tried to follow it in before McGregor punched clear on the goal-line, United unable to make anything of the rebound.
Daly and Naismith tussle for the ball during the first half
Nacho Novo came on in place of Fleck and gave Rangers more attacking impetus with the Spaniard involved in a move that ended with Lafferty lifting a shot over the crossbar.
Andrew Little then sent a tame effort into the arms of keeper Dusan Pernis from 10 yards out.
Lafferty limped off to be replaced by Kenny Miller and the striker forced a save from Pernis moments before almost getting on the end of an inviting DaMarcus Beasley delivery.
Goodwillie latched on to a lofted ball into the box and nicked it past McGregor but the striker's celebrations were cut short by the linesman's flag.
McGregor made an excellent save to tip Daly's header from Robertson's free-kick away from goal moments before United finally made the breakthrough.
Danny Wilson's clearance ricocheted off an opponent high into the air and Robertson again followed in as McGregor came off his line but this time the midfielder got the crucial contact to scramble the ball into the net.
Wilson's header was collected by Pernis as Rangers' late rally failed to yield a score.
90:00+3:11 The final whistle is blown by the referee.
90:00+2:03 Jon Daly is caught offside. Free kick taken by Allan McGregor.
90:00+0:59 David Robertson gives away a free kick for an unfair challenge on DaMarcus Beasley. The ball is delivered by DaMarcus Beasley,
Danny Wilson takes a shot. Dusan Pernis makes a save.
90:00+0:25 Substitution (Rangers) makes a substitution, with Kris Boyd coming on for Andrew Little.
90:00+0:14 Booking Booking for David Goodwillie for unsporting behaviour.
89:11 GOAL - David Robertson:Dundee Utd 1 - 0 Rangers Goal scored by David Robertson from inside the six-yard box to the bottom right corner of the goal. Dundee Utd 1-0 Rangers.
88:42 Centre by David Robertson, Jon Daly takes a shot. Save by Allan McGregor.
87:11 Inswinging corner taken from the left by-line by Craig Conway, Allan McGregor makes a save.
86:57 Nacho Novo concedes a free kick for a foul on Darren Dods. Free kick taken by Garry Kenneth.
86:38 The referee blows for offside. Allan McGregor restarts play with the free kick.
84:17 Foul by Steven Naismith on Daniel Swanson, free kick awarded. Daniel Swanson produces a cross, Header by Darren Dods from
deep inside the penalty area misses to the right of the target.
82:35 Outswinging corner taken from the left by-line by DaMarcus Beasley.
82:02 The assistant referee flags for offside against David Goodwillie. Free kick taken by Allan McGregor.
81:40 Kenny Miller takes a shot. Dusan Pernis makes a comfortable save.
79:57 Free kick crossed by Craig Conway, Sasa Papac makes a clearance.
79:57 Booking Booking for Steven Naismith.
79:40 Steven Naismith challenges Craig Conway unfairly and gives away a free kick.
78:47 Effort from outside the box by Daniel Swanson goes wide right of the target.
76:24 Free kick awarded for an unfair challenge on Craig Conway by Steven Whittaker. Free kick taken by Sean Dillon.
Correction - 75:31 Substitution Kenny Miller comes on in place of Kyle Lafferty.
75:31 Substitution Kenny Miller comes on in place of Kyle Lafferty.
72:57 Andrew Little takes a shot. Dusan Pernis makes a comfortable save.
72:17 Substitution Daniel Swanson replaces Morgaro Gomis.
69:50 Shot on goal by Kyle Lafferty from long range goes harmlessly over the target.
68:22 Substitution Nacho Novo is brought on as a substitute for John Fleck.
67:56 Corner taken by Craig Conway.
67:41 The ball is swung over by Keith Watson, clearance by Steven Naismith.
65:55 Free kick awarded for a foul by Steven Naismith on Craig Conway. Sean Dillon takes the direct free kick.
63:26 Jon Daly is ruled offside. Danny Wilson takes the indirect free kick.
60:13 Steven Naismith challenges David Robertson unfairly and gives away a free kick. Craig Conway delivers the ball from the free
kick right-footed from left channel, Sasa Papac manages to make a clearance.
56:28 David Robertson takes a shot from close range that hits the post.
54:02 Foul by Keith Watson on DaMarcus Beasley, free kick awarded. Sasa Papac takes the direct free kick.
51:45 The ball is delivered by Craig Conway, clearance by Danny Wilson.
48:30 Handball decision goes against David Goodwillie. Free kick taken by Allan McGregor.
46:54 Steven Naismith gives away a free kick for an unfair challenge on David Robertson. Free kick crossed right-footed by Craig
Conway from right wing, clearance made by David Weir.
46:39 The ball is crossed by Craig Conway.
45:47 Andrew Little produces a right-footed shot from close range which goes wide of the right-hand upright.
45:01 The match restarts for the second half.
45:00+1:53 The referee calls an end to the first half.
45:00+1:13 Substitution Keith Watson comes on in place of Mihael Kovacevic.
43:35 Effort from 20 yards by Darren Dods. Allan McGregor makes a comfortable save.
42:25 The offside flag is raised against John Fleck. Free kick taken by Dusan Pernis.
40:42 The referee blows for offside against Craig Conway. Indirect free kick taken by Allan McGregor.
37:31 Corner taken by Craig Conway, clearance made by David Weir.
37:18 A cross is delivered by Craig Conway, clearance made by David Weir.
36:39 Free kick awarded for a foul by Sasa Papac on David Goodwillie. Prince Buaben crosses the ball in from the free kick, David
Weir manages to make a clearance.
34:52 Free kick taken by Danny Wilson.
34:52 Booking David Robertson is shown a yellow card.
34:37 David Robertson challenges Maurice Edu unfairly and gives away a free kick.
33:24 Mihael Kovacevic gives away a free kick for an unfair challenge on DaMarcus Beasley. Sasa Papac takes the free kick.
31:44 Outswinging corner taken right-footed by Craig Conway, Danny Wilson manages to make a clearance.
31:27 Inswinging corner taken right-footed by Craig Conway, clearance by David Weir.
31:17 Booking Garry Kenneth receives a caution.
30:06 Handball decision goes against DaMarcus Beasley. The free kick is swung in right-footed by Craig Conway.
29:14 Kyle Lafferty is caught offside. Dusan Pernis takes the free kick.
28:52 Handball decision goes against Morgaro Gomis. Direct free kick taken by Danny Wilson.
28:09 Free kick awarded for a foul by Craig Conway on DaMarcus Beasley. Free kick crossed left-footed by John Fleck from right wing,
Sean Dillon makes a clearance.
27:05 Garry Kenneth takes a shot. Save by Allan McGregor.
26:49 Corner from the left by-line taken by Craig Conway, clearance made by David Weir.
26:40 David Goodwillie sends in a cross, Danny Wilson gets a block in.
24:01 Shot by Craig Conway from deep inside the penalty area misses to the right of the target.
22:54 The ball is delivered by Garry Kenneth.
21:44 Inswinging corner taken right-footed by Craig Conway from the left by-line, clearance made by David Weir.
19:36 Shot on goal by Prince Buaben from just inside the area goes over the target.
15:12 Sean Dillon concedes a free kick for a foul on DaMarcus Beasley. Allan McGregor takes the free kick.
9:40 Unfair challenge on Garry Kenneth by Andrew Little results in a free kick. Free kick taken by Garry Kenneth.
8:03 The offside flag is raised against Andrew Little. Free kick taken by Dusan Pernis.
7:31 Unfair challenge on Kyle Lafferty by Morgaro Gomis results in a free kick. Steven Naismith takes the free kick.
5:36 Mihael Kovacevic produces a right-footed shot from just outside the penalty box that misses to the left of the target.
4:53 John Fleck takes a shot. Blocked by David Weir.
4:23 Craig Conway produces a cross.
2:38 Craig Conway has an effort at goal from just outside the penalty box which goes wide of the left-hand post.
1:22 Outswinging corner taken by Craig Conway from the right by-line, Morgaro Gomis takes a shot. Blocked by David Weir.
1:06 Jon Daly takes a shot. Save made by Allan McGregor.
0:00 The referee gets the match started.
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