Defoe showed why he is rated one of the best strikers in the country with the only goal of the game and gave chairman Daniel Levy a glimmer of hope after he promised supporters the glory days will return next season.
Levy gave an honest assessment of the club's troubled season before their final home game and was the first to admit how disappointing the year has been and promised wholesale changes.
Not only have Spurs fans had to endure a miserable season where the team have been without a manager since Glenn Hoddle was handed the sack last September.
But they were forced to watch their arch rivals Arsenal win the Premiership title on their hallow turf and add insult to what has been a season to forget for the Tottenham supporters.
Levy in his programme notes insisted the poor levels of performance were not acceptable to him and they have had an appalling finish to the season which has seen them just avoid a relegation struggle.
Confusion still surrounds the identity of the new manager and whether current caretaker boss David Pleat will be allowed to continue his role as Director of Football.
Martin O'Neill and Italian coach Giovanni Trapattoni still remain the favourites to take over the managerial hot-seat and how Spurs fans must be praying a high-profile name is appointed during the summer.
Whichever manager is brought in during the summer, there will need to be some major re-building work as the new man looks to impose his own style on the club. And Levy knows his next appointment will be crucial for the club's long-term future.
Several players including the likes of Gus Poyet, Darren Anderton, Christian Ziege and club skipper Jamie Redknapp are all out of contract at the end of the season and looked to be making their last appearance at White Hart Lane.
And how the Tottenham fans must have wished this last game had come a few months earlier, despite Defoe's winner after witnessing one of the worst periods in the club history.
The one glimmer has been the signing of the England forward Defoe, who has clearly not given up hope of boarding the plane for Euro 2004.
Defoe, who made a £7.5million move from West Ham in January proved the matchwinner once again when he netted his 23rd goal of the season on 17 minutes.
Ledley King's ball over the top of the Blackburn defence fell perfectly into the path of Defoe who fired a sweet left-foot shot past Peter Enckelman who was making his debut for Blackburn.
Blackburn forced their way back into the game and could have snatched an equaliser on 40 minutes when Garry Flitcroft's cross from the right fell perfectly for Andy Cole who rose above Stephen Kelly, but saw his close-range header flash just wide.
Robbie Keane should have scored on 43 minutes when he weaved his way into the box and saw his left-foot shot produce a superb save from Enckelman.
Blackburn had three golden opportunities to get back on level terms within the opening seven minutes of the second half.
Tottenham defender made a hash of trying to clear the ball on 48 minutes and was dispossessed by Cole who fed the ball to his strike partner Jonathan Stead.
But with the goal at his mercy, the young striker somehow managed to fire the ball wide of the post.
The former Huddersfield striker was involved in the heart of the action again just two minutes later when he raced on to a Lucas Neill throughball and forced another fine save from Kasey Keller diving away to his left.
Souness must have thought it was not going to be his day on 52 minutes when Tugay's corner found Jonathan Douglas completely unmarked inside the box, but he planted his header wide.
Robbie Keane came close again to adding a second for the home side on 70 minutes when he rose the highest to meet a Defoe cross, but saw his header come back off the crossbar.
And German international Ziege came even closer to sealing all three points for the home side on 75 minutes when his shot was cleared off the line by Michael Gray.
But Tottenham managed to hold on for all three points.
Man-of-the-match: Tottenham's frontman Jermain Defoe was in excellent form leading the front line and scored the match winner on 18 minutes.