After losing 7-0 on aggregate to Bayern Munich in last season's Champions League semi-finals, it became abundantly clear that Barcelona needed to spend some serious money on a new centre-back, and specifically on Chelsea's David Luiz.
The Catalan giants had been ruthlessly carved open time and again by the Bavarians, who celebrated a shift in power from Spain to Germany over the course of that two-legged tie.
Bayern Munich gave Barcelona a taste of their own medicine by pressing them high up the pitch, while the centre-back pairing of Gerard Pique and Marc Bartra simply couldn't cope with Bayern's devastating attack.
Of course, Barcelona's defensive frailties were down to more than the performances of their two centre-backs, but clearly they lacked strength in depth in that particularly area of the pitch.
With Carles Puyol not getting any younger, this summer had to be the time when Barcelona brought in a new top-class central defender to boost their hopes of becoming Champions League challengers again.
Instead, rather inexplicably, they spent their entire £50m budget on Neymar - leaving them with no money to strengthen their vulnerable defence, and subsequently no chance of winning the Champions League.
Even though they have Neymar, Andres Iniesta and the world's best player Lionel Messi, Barcelona will still be carved open as soon as they come up against a decent European outfit this term.
Yet they could have gone some way to preventing this by shelling out around £40m for Chelsea's flamboyant defender Luiz, who would have complimented Barcelona's style of play perfectly.
The Brazilian is comfortable in possession, assured when coming out of defence with the ball and has the pace to recover from compromising situations.
A centre-back partnership between Luiz and Pique could have blossomed into something special - and left Barcelona much more solid at the back.
Javier Mascherano has performed admirably for Barcelona since being converted into a centre-back at the Nou Camp, but the tenacious Argentine pales in comparison to Luiz as a central defender.
Barcelona's failure to address their main weakness is likely to cost them dearly this season.