For the second time in four days, Steve Campbell's side suffered the agony of conceding a last minute goal to consign them to defeat at St Andrews this afternoon.
However, whereas against Inverness Caley Thistle, a draw would have been deserved, this time, overall, there could be few complaints that Rangers deserved to win, based on them having totally dominated the opening period.
Indeed, only some wayward finishing and a terrific saves by United keeper Marc McCallum to deny Kal Naismith and Rhys McCabe prevented this re-arranged League clash being over as a contest by the interval.
If the Tangerines were lucky to survive that first half onslaught, there was nothing flukey about Stuart Armstrong's equaliser three minutes from half time when he drifted past two defenders before slipping the ball under the keeper.
However, despite all the visitors' attempts at goal, the one that did count after 17 minutes was not only speculative but heavy on good fortune. Kamil Wiktorski's pop at goal from 35 yards didn't look all that menacing, but took a wicked deflection to leave McCallum helpless.
Second half was a much more even affair, albeit Rangers did create the more clear-cut chances. A Maxie Wright effort was blocked by McCallum's legs, but five minutes later, a surging run by Robert Thomson was blocked with United having genuine grounds for complaint that it should have been a penalty.
With just over 20 minutes left, a powerful Naismith header was tipped over, but at the other end, Michael Lee twice failed to hit the target from a good position.
The game appeared to be drifting to a draw when United ceded possession when attacking, with just over a minute left. Rangers raced to the other end and substitute Ant Marenghi squeezed in a Naismith cutback from the right at the near post.
It was a cruel ending to a much improved second half performance.
Team: McCallum, Shaw, Barrett, Young, Mosson, Lee, W Robertson, Stokes, Armstrong, R Thomson, Elfverson (Campbell 84).