Ozan Tufan's penalty blunder left Hull facing a mammoth task to make the play-offs after a 0-0 draw at Watford.
Home keeper Daniel Bachmann saved the Turkish forward's spot-kick in the 11th minute of a lacklustre match and now the Tigers, who have three games to play, are six points off the top six.
Hull had started the day desperate for points to keep in touch with the promotion pack.
Fifth-placed West Brom's defeat at Leicester in the lunchtime kick-off gave the Tigers an extra incentive and they looked full of purpose at the start.
Watford were given a taste of what to expect when Matty Jacob's well-flighted pass to Jaden Philogene completely took out right-back Ryan Andrews. Unfortunately for Philogene, his cross was easily gathered by Bachmann.
Soon after, Philogene earned a talking-to from referee Ben Toner for bundling over Hornets defender Ryan Porteous in the Watford penalty area.
Then Hull were were presented with a golden opportunity - and wasted it.
Abdulkadir Omur and Tufan combined to send Fabio Carvalho racing into the box from the left, where Wesley Hoedt brought him down.
Tufan, who had an unsuccessful loan at Watford in the Premier League in 2021-22, stepped up to take the spot-kick in front of the home end and was taunted by the Hornets supporters.
That might have unnerved him - or it could have been Watford's defenders agitating because the ball was not on the penalty spot - but Bachmann guessed correctly, diving to his left to keep out the kick to the joy of the home fans.
Predictably, that fired up Watford, with Yaser Asprilla and Emmanuel Dennis trying their luck.
But the visitors always looked more dangerous in the final third, and Bachmann rescued the Hornets again midway through the first half. Tufan came
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