Charlie Adam’s goal early in the second half looked set to give Rangers a vital away victory as they continue their desperate pursuit of Celtic at the top of the SPL but lapses in concentration again cost the Ibrox side dearly and they now sit 15 points behind their oldest rivals just one week into November.
Wednesday’s CIS Cup tie with St Johnstone now takes on extra significance with the prospect of Le Guen lifting the league championship on his debut season becoming increasingly remote.
The manager had chosen to tinker again with his starting line-up despite the impressive result and performance against Haifa in the UEFA Cup.
Sasa Papac, ineligible for European competition, replaced the unfortunate Karl Svensson who dropped to the bench – Julien Rodriguez was nowhere to be seen – while up front Thomas Buffel came in for Kris Boyd.
Looking to put together two consecutive victories – something that would almost constitute a run these days – Rangers began brightly and Nacho Novo should have done better than scoop an effort over the bar after being expertly picked up by Barry Ferguson.
Ferguson then shot wide as Le Guen’s side looked to put United under the screw right from kick-off.
Craig Levein, in his first game in charge since succeeding Craig Brewster as Tannadice boss, made seven changes to his starting line-up, and sent his beleaguered side out in a defensive-minded formation with only one striker, Collin Samuel, at its pivot.
It put the onus on Rangers to try to break down the side currently residing at the foot of the table, something they struggled to do in the first half despite dominating play for large spells.
Allan McGregor, again in for the injured Lionel Letizi, was virtually a spectator as United seemed content to allow Rangers possession and hope to hold out for a point.
It took Rangers until the 34th minute to record another effort on target, Novo dragging a shot wide from a promising position after good build-up play from Adam and then Alan Hutton before, just a minute later, Prso chose a hopeful ball across the box when a shot looked the better option.
United, having spent the bulk of the half defending, finally ventured forward as half-time approached and were almost rewarded for their boldness when Samuel’s cross was almost inadvertently turned into his own goal by Papac.
From the resultant corner, David Robertson’s thumping volley was expertly turned away by McGregor in what was the last piece of action of an uneventful first half.
United, with teenage striker David Goodwillie on for Samuel, continued to take the play to Rangers and paid for their bravery when the Light Blues broke on the counter attack and went in front five minutes after the re-start.
Buffel’s pass sent Novo clear down the left wing and when his centre duly arrived Adam was there to sweep it past Derek Stillie for his fourth goal in five games.
Bolstered by his strike, Adam almost had a second when he fastened onto Ferguson’s reverse ball and attempted a cute chip over Stillie who had to stretch fully to get a touch to keep out the goal bound effort.
Rangers, though, were nearly undone by another individual error. Jeremy Clement, understandably tiring, inexplicably passed straight to Goodwillie who in turn played the ball wide to Barry Robson.
His cut back was perfect for the in-rushing Craig Conway but he snatched at the shot and blazed it high over McGregor’s bar.
Rangers’ response was a Novo turn and shot that squirmed narrowly wide and then another fierce Adam drive that Stillie did well to palm skywards.
Despite Rangers’ dominance, however, there was always that nagging suspicion that United could claw their way back into it and sure enough it happened with 13 minutes to go.
A series of corners concluded with Robson swinging a delivery to the back post where Garry Kenneth rose above Prso to nod the ball beyond McGregor for the equalising goal.
It was as disappointing as it was predictable. Rangers wobbled for a period afterwards – Goodwillie came close to putting United in front – before Adam burst through the middle to feed Kris Boyd who in turn found Novo who had crept into an offside position.
United, though, had grown in stature since their goal and went in front after 82 minutes. Mark Kerr’s free kick was played into the heart of the box where Lee Mair was allowed to drift in unmarked to head past McGregor for what turned out to be the winning goal.
DUNDEE UNITED (4-5-1): 1 Stillie; 5 Mair, 3 McCracken, 18 Kenneth, 2 Kalvanes; 15 Conway, 7 Kerr, 17 Cameron, 25 Robertson, 11 Robson; 20 Samuel (Goodwillie 46)
Subs not used: McLean, Archibald, Duff, Easton, Burnett, Smith
Booked: McCracken (86)
RANGERS (4-3-3): 22 McGregor; 20 Hutton, 5 Papac, 7 Hemdani, 26 Smith (Sebo 85); 8 Clement, 6 Ferguson, 25 Adam; 10 Novo, 4 Buffel (Boyd 66), 9 Prso
Subs not used: Klos, Bardsley, Rae, Svensson, , Stanger
Booked: Prso (86)