Yes, he'd had a decent stint with the club's B team - but that is hardly the sort of experience that you'd expect to ready a man for a spell at the helm of one of the world's greatest sporting insitutions.
Yet that gamble paid off spectacularly for Barca; since then, the club have never looked back, while Guardiola himself has gone on to prove an equally stunning success at Bayern Munich.
Here's a look at Guardiola's career, and what he has achieved in his various roles.
Guardiola took over a demoralised second-side that had just been relegated to its lowest tier in over 30 years. But he successfully took a squad of players who had been underperforming and returned them to their proper level, winning the league.
- Tercera División champions: 2007–08
Pep Guardiola in his rather more hirsute Barcelona B days
Image credit: AFP
Frank Rijkaard had been a huge success at Barcelona, leading the side to two league titles and a Champions League, and bringing through players such as Lionel Messi, Xavi and Andres Iniesta. But the team seemed on the wane in the summer of 2008: after two successive trophyless seasons, Rijkaard was jettisoned and Barca chiefs took a punt on Guardiola.
The difference was extraordinary. Guardiola's team played a brand of football that took European football by storm. Barca won the league by nine points, claimed the Copa del Rey, and wrapped it up with a victory in the Champions League final - securing the first ever treble in Barcelona's illustrious history.
Guardiola's Barca ended up claiming three successive league titles, two Copa del Rey trophies and two Champions League victories - as well as the other assorted trinkets available to European champions, such as a couple of European Super Cups, three Spanish Supercopas, and two Club World Cups. 14 trophies in just four seasons.
- La Liga champions (3): 2008–09, 2009–10, 2010–11
- Champions League winners (2): 2008–09, 2010–11
- Copa del Rey winners (2): 2008–09, 2011–12
- FIFA Club World Cup winners (2): 2009, 2011
- European Super Cup winners (2): 2009, 2011
- Spanish Supercopa winners (3): 2009, 2010, 2011
Lionel Messi and Thierry Henry helped Barcelona to the treble in 2009
Image credit: Eurosport
If ever a job seemed like a double-edged sword this was it: in 2013, after a year's sabbatical Guardiola inherited from Jupp Heynckes a team that had just won the treble. And while Bayern haven't matched that achievement on Guardiola's watch, they won the Bundesliga and DFB Pokal cup titles in his first season, and won the league again last season.
What's more, they remain on course for another league title - they are eight points clear at the time of writing - and have every chance of more cup glory. Having scooped the European Super Cup and Club World Cup shortly after arriving in Bavaria, Guardiola has five trophies to his name in two seasons. In a few months' time that could end up as a record of eight in three seasons.
- Bundesliga champions (2): 2013–14, 2014–15
- DFB-Pokal winners (1): 2013–14
- UEFA Super Cup winners (1): 2013
- FIFA Club World Cup winners (1): 2013
Total trophy record
League victories: Six (2007–08, 2008–09, 2009–10, 2010–11, 2013–14, 2014–15)
Champions League victories: Two (2008-09, 2010-11)
Domestic cup victories: Three (2008–09, 2011–12)
Supercup/Club World Cup victories: Nine (2009 x3, 2010 x1, 2011 x3, 2013 x2)
Grand total in six seasons as a manager: 20
It remains to be seen whether Bayern's players will continue to follow their manager into battle in quite the same way now they know that not only is he leaving, but also where he is going.
Manchester City won't care either way. A club that has picked up just two leagues and one of each domestic cup plus a Community Shield in its last five seasons has just brought on board a manager who seems to collect silverware as easily as most of us collect supermarket loyalty card points.
Guardiola does have a fair bit to prove, however. Some have argued that at Barcelona he took over a team full of staggering talent, and merely got them working as they should have been already; and that at Bayern he took over an all-conquering team and merely kept them on course.
Yet to speak about both of those achievements as if they are somehow easy is absurd: indeed, it actually rams home just how much he could do for City. The 2012 and 2014 Premier League champions clearly have abundant talent that has not been harnessed to its fullest; and equally, they have struggled to retain momentum and build on success.
Both of those faults are likely to be addressed handsomely by Guardiola - and the very fact of his appointment may well convince Manchester United's chiefs that the only possible counter-move is to bring in Jose Mourinho as the new manager up the road at Old Trafford. The next few seasons in English football could prove very interesting indeed.
2011-12 Premier League Manchester City celebrate with trophy. More of this to come?
Image credit: PA Photos