A late Gary Mackay-Steven strike dented Inverness Caledonian Thistle's chances of reaching a Europa League slot and sealed an away win for Dundee United.
Billy McKay's penalty was saved by Radoslaw Cierzniak before Aaron Doran put Inverness into a 42nd-minute lead with a right-footed shot.
Ryan Dow converted Jon Daly's knock-down to level the scores after restart.
With 10 minutes remaining Doran blasted a sterling chance over the stand before Mackay-Steven's injury-time strike.
Inverness will now have to battle to secure third place in the Scottish Premier League and the valuable European football slot that comes with it next Sunday in the highland derby away to their Highland rivals Ross County, who are still within reach of the same target.
The match started brightly enough for the hosts, with Andrew Shinnie's 4th-minute shot deflected for a corner.
United hit back with a powerful drive by Stuart Armstrong in the 12th minute, but Caley keeper Reguero got a strong hand to it to block.
Brian McLean made a great recovery tackle to clear a yard from goal on 18 minutes as Inverness looked determined to find the net.
McKay should have scored from 12 yards after 33 minutes minutes, but Cierznak dived low to his right to push the ball wide.
Moments later, the home side won a penalty after John Rankin was penalised for a challenge on Doran.
McKay struck a powerful shot from the spot, but Cierznak's leap to the left was spectacularly acrobatic and he beat the ball away for a top-class save.
Inverness eventually did find the net as half-time approached when Doran, with his back to goal, swivelled to hit a sweet low shot from the edge of the box that flew past Cierznak's outstretched hand to nestle inside the right hand post.
United were back on level terms five minutes after the restart when Dow raced on to a knock-down to blast a volley low past Reguero.
Johnny Russell had a great chance to put the visitors further ahead moments later, but failed to connect with the ball 12 yards from goal.
Russell then tested the keeper with a speculative 30-yard lob, but Reguero held well under the bar.
Jon Daly headed just wide as full-time approached, but United were not to be denied, and, as the match entered stoppage time the Terrors broke away on the right and Stuart Armstrong's low cross was side footed home by Gary Mackay-Steven.
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