Sheffield United restored a seven-point cushion in the race for automatic promotion after an own goal from Ryan Porteous sealed a 1-0 victory against Championship play-off hopefuls Watford.
After a tense first half failed to produce a shot on target from either side, Porteous diverted the winner into his own net after reacting to a header from Oli McBurnie.
Earlier an offside flag denied Jayden Bogle from heading the hosts in front just after the hour mark.
Watford goalkeeper Daniel Bachmann made crucial saves either side of that effort being ruled out - first denying Oliver Norwood from a free-kick before coming up with a double save to foil substitutes Tommy Doyle and Ben Osborn.