AS far as bad days at the office go, this was a shocker for Saints. They can't afford any more.
Backed by more than 2,000 travelling fans, who turned their end into a sea of yellow and blue and were in the mood for a party, it was a wretched performance.
It certainly wasn't the worst of the season - which perhaps shows how bad 2004/05 has been. But it was bad.
In fairness to the side that played on Saturday, it's the first time they've had an off-day of this proportion since the January transfer window slammed shut.
They've performed admirably of late and picked up points.
But for the first time, this was Harry's team that played badly.
It was impossible to criticise individuals for the performance either: it was the entire team that were below par.
What will count now is how this side recovers from the setback.
It was dreadful, but there's no point in dwelling on it - they just have to make sure it doesn't happen again or Saints' proud 27-year stay in the top flight of English football will come under increasing threat.
Next week's match against Aston Villa is now more vital than ever.
Saturday's Ewood Park shocker means nothing short of a win at St Mary's will do against a Villa team held at home by lowly West Brom yesterday.
But Saints are still well capable of getting the three points. They just need to make sure they don't implode like they did against a Blackburn side who had only won three of their previous 15 home league matches.
In fairness to Redknapp, he held his hands up after the game for playing three up front in the second half and inviting Rovers to attack on the counter, but it was worth a go.
The main question before the match was whether Redknapp would stick with Henri Camara or bring in Kevin Phillips.
Camara made a stunning start to life as a Saint but has not been too impressive for a few games now, while Phillips had impressed coming off the bench.
In the end, the need for pace away from home made Redknapp decide to stick with Camara - but the on-loan striker did him few favours in return.
Like they were against Chelsea a week earlier, Saints were up against a 4-5-1 formation at Ewood Park.
When you play teams who have that formation, the plan is to match their five in middle man for man so you don't get overrun in the centre.
That means that while Peter Crouch plays on the shoulder of the last defender, the other striker - in this case Camara - has to spin off the midfielder who sits deep just in front of the back four.
Unfortunately, the Senegalese forward was unable to adapt his game to do that and, like against Claude Makelele for Chelsea, Blackburn's Aaron Mokoena was able to shield his defence and Saints were outnumbered in midfield.
Whatever team Redknapp put out, he couldn't have expected them to play like this - albeit against an impressive Rovers side who before Saints' visit had scored less home goals than anyone in the Premiership with the exception of West Brom and Palace.
Blackburn took the lead on 11 minutes when Rory Delap allowed Morten Gamst Pedersen to get in behind him and latch onto a long Mokoena ball.
The Rovers wideman took a touch that pushed him wide but still fired in past Paul Smith, deputising for the injured Antti Niemi, who had pulled a hip muscle in training on Friday.
Rovers continued to dominate and it took 40 minutes for Saints to get a shot on target - a tame Crouch volley from distance.
Saints went in at half-time relieved to be just 1-0 down.
But after the interval it didn't take long before Saints, now playing Crouch, Camara and Phillips in attack, conceded again.
Steven Reid got in behind Olivier Bernard and squared into the area, where Andreas Jakobsson, sliding in at the near post, deflected the ball into his own net.
On 55 minutes it got worse. Saints couldn't clear a corner from inside their area and, when the ball was pulled back to Reid who had evaded the attentions of Claus Lundekvam, he easily slotted home.
Saints' best chance fell to Camara in the first half but his shot flew wide of the post.
The only other chances of note for Redknapp's men saw Crouch head wide and Phillips at least make Brad Friedel make a save of note with eight minutes left.
This really was an afternoon to forget, but the battle for survival means the result has to be put to bed now by everybody at the club and outside it.
It was a terrible performance, but perhaps Saints were due a below par display after recent heroics.
This should prove to be a bizarre blip rather the beginning of the end.