For so long it seemed as if this was going to be the season when Tottenham's long-awaited arrival in the big time would be confirmed, yet it is ending on a note that puts their promise into deepening shade.
While Champions League heroics against AC Milan and Inter gave Spurs fans every right to believe their time to mix it with the game's true giants had finally arrived, their end of season slump suggests too many members of Redknapp's squad are not up to the job at the highest level.
Wigan, West Ham, West Brom and now plucky Blackpool have all left White Hart Lane with something to celebrate this term, with Tottenham's inability to kill off lesser opponents costing them a chance of challenging Manchester City for fourth spot in the Premier League.
Even on a day when their chief rivals had slipped up by losing at Everton, Spurs seemed incapable of lifting themselves and now face the prospect of not having European football in their diaries at all next season, with Liverpool emerging as favourites to finish fifth in the league and claim a Europa League spot.
Whether the rumblings of discontent that Tottenham supporters have started to direct at Redknapp will now develop into something more concerted remains to be seen after this latest lacklustre performance that could so easily have finished with an embarrassing home defeat, after Charlie Adam edged his battlers to the brink of a famous victory with his 75th-minute penalty.
The fact that the Scot had missed from the spot from another penalty a mere 70 seconds before his opening goal said much about his character, yet it was not to be a winner as Jermain Defoe salvaged a points for Spurs with an 88th-minute strike that did nothing to boost their hopes of qualifying for Europe's elite competition next year.
Since Gareth Bale and Rafael van der Vaart have run out of steam in recent weeks, and stopped carrying team-mates who over-achieved in the first half of the season, Spurs have fluffed their lines on a weekly basis and Redknapp now has to halt their slide before it becomes terminal.
Back in the days when mediocrity was accepted with a little too much eagerness by Spurs supporters whose expectations had been diluted by years of frustration, the likes of Defoe established himself as heroes of the White Hart Lane faithful, who were willing to ignore the glaring holes in the make-up of a striker whose reputation has long been greater than his talent.
Yet in a campaign when the likes of 'keeper Heurelho Gomes, defender Vedran Corluka, midfielder Jermaine Jenas and his namesake Defoe have fallen well short of what is expected from top-class performers, Tottenham's hopes of a top-four finish have run aground.
To be fair to Defoe, his late goal was the only highlight on a dire afternoon for Spurs that started with a half-hearted opening 45 minutes notable for little more than a fine save from Gomes from Adam's stinging 23rd-minute volley and a Defoe strike ruled out, inevitably, by a linesman's flag.
Roman Pavlyuchenko was equally culpable of failing to make the right runs to test Blackpool's surprisingly untroubled back-line in the first half and thus has been the primary problem for Tottenham this season, with Defoe, Crouch and Russian hit-man Pavlyuchenko scoring a mere 16 goals between them.
Spurs improved a little after Aaron Lennon replaced Pavlyuchenko at the break, but a handball in the box from Michael Dawson after 74 minutes gave Adam his first chance to first Blackpool into the lead from the spot.
Gomes did well to save as he sprawled to his left, yet the accident-prone Brazilian's excitement got the better of him as dropped the ball from the subsequent corner and stumbled into Gary Taylor-Fletcher to give Blackpool another penalty chance. DJ Campbell argued he should take the second spot kick, but it was Adam who held his nerve to convert with ease.
With Spurs looking increasingly desperate and lacking any inspiration, their fate seemed sealed until Defoe's late shot screamed past Matthew Gilks from 25 yards, to leave the always colourful Ian Holloway to ponder his side's fate with typically jovial comments.
"This performance shows how far Blackpool have come and don't even begin to write us off in this survival fight," he said. "How can I be disappointed that we have left White Hart Lane with a point, against a top class Tottenham side who have been tearing up the Premier League this season? Yes it's a shame to let a late goal in, but this is a great point, let's keep it real.
"We will probably have to go to Manchester United on the last day of the season and pull something off and why not go for it? Let's not be down about this. We are Blackpool, playing in the Premier League with a £10 million budget and we are still in with a chance of staying there. It's incredible."
Harry Redknapp accepted his side's Champions League hopes are now dead, as he hinted at big changes to his squad in the off-season. "This was a game we had to win and yet we have struggled to score goals at home in recent weeks and that has hurt us," the always chirpy Spurs boss said.
"Our strikers have not scored goals this season and it is difficult to put our finger on why that has happened. We have thrown it away in the last eight or nine games and we haven't been the same team in the last bit of the season. We had half a chance of getting back into the top four after City lost today, but it's tough now.
"We haven't been good enough to finish in the top four this season and it may be that we need to get the fringe players out of our squad here. We have a lot of players of a similar standard here, so we need to look at the players and try to bring in a couple of top-class players. That's the aim this summer."
It's not merely the fact that his side have failed to reclaim a top-four spot that will alarm Redknapp, but the manner of his side's end-of-season collapse that sends out a note of genuine alarm. His suggestion that a major squad shake-up is now on his mind confirms he is ready to ease the pain of Spurs followers.
In truth, there are too many mid-table performers in his ranks right now and they need to be removed, yet Redknapp's failure to conjure up a second season of Champions League football may mean some of the stars he would want to keep will be joining the likes of Defoe by heading for the exit door. As for Blackpool, their remarkable story continues to roll and roll.
MAN OF THE MATCH: Charlie Adam. He may have been lucky to stay on the field after his savage second-half challenge on Gareth Bale, but his class and composure shone through the heroic Blackpool effort.
PROGRAMME TRIUMPH: The Spurs media team deserve credit for producing a magnificent matchday programme for this fixture, which was a fitting tribute to the 50th anniversary celebrations to commemorate the club's 1961 Double triumph. What a shame the Tottenham class of 2011 went missing on this significant date.
BALE UPDATE: Spurs boss Harry Redknapp fears Gareth Bale serious suffered ankle ligament damage after a brutal challenge from Adam left him screaming in agony.
SPURS VERDICT: The wheels have fallen off the Spurs bandwagon and boss Redknapp seems incapable of halting their slide. A summer of concern lies ahead for all of his club's supporters.
BLACKPOOL VERDICT: Holloway's men have now taken four points from Spurs in the last couple of months and a win at home to Bolton next weekend may just keep them in the Premier League for another season.