Big Sam is back
Allardyce cited a desire to win trophies as the reason why he walked out of one of football's more secure positions.
Inextricably linked to this was his ambition to manage the England team. He had impressed the Football Association board when he was interviewed in 2006 but lost out to Steve McClaren and felt that managing a high-profile club would enhance his prospects.
He might have established Bolton in the Premier League, taken them to a Carling Cup final and into the Uefa Cup but he lasted less than nine months at Newcastle and the challenge facing him now is one of restoring his damaged reputation.
The 54-year-old had expressed his interest in several jobs after leaving St James Park - not least the vacancy at Sunderland - but it is Blackburn chairman John Williams who has finally offered Allardyce the opportunity he had so desperately craved.
Quite simply, both Allardyce and Blackburn need each other.
Rovers are a proud Lancashire club but hardly rich by the heady standards of the Premier League and have, at best, a modest fanbase. With so many other clubs competing for breathing space in Lancashire they compete in a very congested county.
It is part of the reason why relegation for Blackburn would be a disaster. The Championship is packed full of clubs who have tasted the top flight, with its attendant cash riches and fat, long contracts, and disappeared without trace after falling through the trapdoor.
Rovers, of course, won promotion back to the Premier League in 2001 after relegation two seasons earlier but the situation is different now. The days of being bankrolled by Jack Walker are long gone and the trust that has owned a 99.8% stake in the club since his death in 2000 is unlikely to continue to invest in the club in the long term.
The trust is also trying to sell the club and have appointed investment bankers Rothschild to try to find a buyer. The damage that relegation would do to their worth is difficult to calculate but would obviously be severe.
This must have been uppermost in the mind of Williams, a pragmatic and shrewd operator who boasts a solid record of managerial appointments. He obviously decided he had made the wrong decision in appointing the inexperienced (certainly at Premier League level) but highly regarded Paul Ince. And in bringing Allardyce to the club the following day he has not only acted with breathtaking decisiveness but signalled an abrupt change of direction.
Allardyce, after all, is hardly an exponent of the beautiful game but he knows how to maximise a modest club's potential in the Premier League. An uncompromising central defender during his playing days, his teams play a direct, physical but effective brand of football. It might go against the grain at a club traditionally regarded for their attractive football (while his long association both as player and manager with Bolton may be a bitter pill to swallow for some Rovers fans) but Williams has appointed the man with the methods ideally suited to their situation.
Blackburn are five points adrift of safety (effectively six given their awful goal difference) and on an 11-game winless streak. The reality of their situation is stark. They need to scrap and harry and fight for every available point over the second half of the season and in Allardyce they have someone who will ensure that they do just that.
And for all that Allardyce's teams lack grace or finesse it cannot be said that Rovers new boss is merely a throwback to the old school.
He forged a reputation at Bolton for his willingness to try new and innovative techniques that improved his squad's performance and extended the careers of senior players such as Gary Speed.
Nutritionists, dieticians, specialists in Chinese medicine, match analysis tool Pro Zone, psychologists - all were hired by Big Sam in an attempt to squeeze a few extra percentage points of performance from his players.
I spoke to Bolton skipper Kevin Nolan regularly during his season as a columnist for this website and he held Allardyce in the very highest regard. Ask him about the composition of the backroom staff, however, and he became a little coy. It was the same with others at the club. They felt that they had a slight advantage and didn't want to give their secrets away. I was told that Allardyce spent some of the money that he might have invested in new players on assembling his backroom team and it will be interesting to see whether he employs the same methods at Ewood.
He also pulled off some surprising and inspired signings at Bolton - the likes of Youri Djorkaeff, Jay-Jay Okocha and Ivan Campo. Will he be able to do the same at Ewood?
First and foremost, though, Allardyce must stop the rot. Half the season remains but in a sense time is not on his side. If the losing streak continues and Rovers lose touch with safety, the manager could be hamstrung before he has even begun.
But there are positives for the new boss.
The swift nature of his appointment means that he has the Christmas fixtures to assess his squad and then the whole of the January transfer window in which to buy and sell.
David Dunn is fit again after an Achilles injury and he has at his disposal a squad that boasts some very decent players. Paul Robinson, Ryan Nelsen, Morten Gamst Pedersen, Matt Derbyshire, Tugay, Benni McCarthy, Christopher Samba, Jason Roberts, Roque Santa Cruz (if he stays) - all are capable of helping Rovers move in the right direction.
It all starts against Stoke on Saturday.
Allardyce and Rovers; it is an intriguing proposition and it should make for fascinating viewing.
One supporter noted after hearing of his club's new appointment that if Allardyce can do for Blackburn what he did at Bolton then it will be a very happy union indeed.
Keeping them in the Premier League would do for starters.