As must-win games go, this was huge for the Hornets as they looked to close the gap on the fourth-from-bottom Latics to four points and everything looked to be going their way when Fitz Hall was sent off and Darius Henderson scored within 25 minutes.
Such was the magnitude of the game though, Watford boss Aidy Boothroyd gambled with an ultra-positive team selection by deciding to name three substitute strikers but no keeper.
It was a decision that looked to have seriously backfired when Ben Foster suffered a leg injury in making a fine double save, rendering him unable to take any kicks for the remainder of the first half.
That would not be an insurmountable problem for most teams, but such is the fragile nature of Watford's confidence the effect was marked, as Foster's booming left boot is a key weapon in their attacking armoury.
The Hornets were reduced to an indecisive, quivering shadow of themselves for the remainder of the opening period and it was no real surprise when Caleb Folan equalised.
Watford did regroup at the break, and Foster recovered, but the game descended into a scrappy battle until the home side sought to capitalise on the visitors' inevitable weakness late on.
Hameur Bouazza and Henderson might have won it, but that would have been harsh on a Latics side that was by the far the happier with the final outcome.
Both sides threatened to trade blows in the opening stages, with the two keepers making saves from Damien Francis and Lee McCulloch respectively, but the game then settled into the fully committed battle most expected until the game took a dramatic twist in the 20th minute.
There was no doubt that Hall had both feet off the ground when he jumped into a midfield tackle on Johan Cavalli, but the fact the defender won the ball and made no real contact with the Frenchman rendered Rob Styles' decision to show a straight red card surprising.
It was certainly a verdict that would not have amused Paul Jewell in the wake of his well-publicised criticism of Phil Dowd following the Latics' recent 2-1 defeat at Arsenal.
But Watford made their numerical advantage count almost instantly. A ball forward from halfway was flicked on by Henderson to Steve Kabba, who had a good shooting opportunity.
He dragged his effort across the face of goal but Jordan Stewart did very well to keep the ball in play and square it back across the six-yard box for Henderson, so long without a goal this season, to bundle in his second in consecutive league games after breaking his duck from the penalty spot at West Ham.
The Hornets looked well set to go on and record only their fourth Premiership win at that point but there then followed a sequence of events that led to a dramatic transformation.
The situation stemmed from Foster making a fine double save to deny Folan and Denny Landzaat, only to suffer a leg injury in the process.
With the England keeper unable to perform any kicking duties, and no replacement on the bench, the confidence visibly drained from the home side and they became almost panic-ridden at times as a catalogue of simple errors were made.
Sensing their opportunity, the Latics equalised five minutes before the interval when an Adrian Mariappa goal-kick was headed back by Matt Jackson, Landzaat hooked the ball forward and Folan got goal-side of Jay DeMerit before prodding the ball past the helpless Foster.
Chances were fewer after the break, as the game increasingly became a question of if Watford could break down Wigan's two disciplined banks of four.
Henderson almost did it in the closing stages when he sent a fizzing 20-yard drive a yard over and then Bouazza went closer still with an improvised effort from tight to the left touchline that almost embarrassed the frantically back-tracking John Filan.