It was inexplicable and inexcusable how the Owls threw away a one-goal lead in the pouring rain at Ewood Park.
Garry Monk's side appeared set to move up to fourth in the Championship after substitute Jacob Murphy opened the scoring against the run of play with seven minutes remaining.
But Wednesday criminally and uncharacteristically switched off at the back as Blackburn scored twice in the final three minutes to earn a first victory in seven outings. John Buckley's winner took a wicked deflection to give Keiren Westwood no chance and spark wild celebrations.
The footballing gods did not shine on the Owls at the other end deep into added on time. They were unlucky not to equalise when Fernando Forestieri, a second half replacement, saw his deflected shot from outside the penalty area hit the post and Sam Hutchinson's follow up was brilliantly saved by Rovers goalkeeper Christian Walton.
Yet the truth is Wednesday's game management was found wanting in the closing stages. To lose after leading in the 83rd minute is not good enough and the reversal is another stark reminder to Monk that this team is a long way off being the finished article.
"It was a real sickener," acknowledged Monk. "We are hugely disappointed.
"In terms of the game, it was exactly what we prepared for. It was a competitive, strong game with both teams pushing each other.
"To be in the position we wanted to be, and prepared for, in the 85th minute – with the goal and the three points - we know we should have seen that game out."
Wednesday did not get their tactics right in East Lancashire. Monk's 4-3-3 set-up (4-5-1 in reality) was overly cautious. Playing Steven Fletcher up front on his own against an out of form Rovers team seemed negative and left the striker far too isolated at times in attack.
There was no spark or creativity in midfield, with Barry Bannan and Massimo Luongo big misses in the centre, and their set plays (the Owls had nine corners in the first half alone) were abysmal.
In a boring first half where Dominic Iorfa had a header cleared off the line by Adarabioyo and Westwood produced a fine stop to keep out Sam Gallagher's header, Blackburn looked there for the taking.
Yet no one took the game by the scruff of the neck for Wednesday. Bannan's ability to dictate proceedings on the ball and his set-piece prowess were sorely missed as they struggled to create chances after the break.
Monk should have brought on Forestieri and Jacob Murphy sooner to give Fletcher some much-needed support.
Westwood was the far busier goalkeeper in the second half and without him the Owls would have trailed by two or three goals before Murphy's opener.
An 88th minute free-kick to the far post saw Adarabioyo rise above Dominic Iorfa and sub Atdhe Nuhiu and loop a header over Westwood.
Moments later, Julian Börner made a hash of a clearance and Joe Rothwell teed up Buckley, who sealed a remarkable fightback.
Monk said: "It was a lack of concentration in that five minutes. A couple of individual mistakes where we got punished, as heavily as you can get punished."
Wednesday have now alarmingly let goals in the final 20 minutes in each of their last three matches on the road. It is a worrying pattern that has emerged and the late concessions against Hull City, Cardiff and Blackburn have seen them drop valuable points and slip out of the play-off positions.
Is it a fitness issue? A lack of concentration? Weak mentality? Not enough leaders in the group? Whatever it is, Monk needs to iron out their problems as soon as possible if they are to stay in touch with the chasing pack.