After a third successive season without winning La Liga, Real Madrid have wasted no time in addressing their weaknesses at the back.
Real conceded 38 goals last campaign, 17 more than champions Barcelona who kept six consecutive clean sheets in the run-up to winning the league. During the same period Carlo Ancelotti's men managed just one despite having an easier run-in, with a 2-2 draw at home to Valencia in gameweek 36 all but handing the title to Barca.
Atletico Madrid's surprise La Liga title win of 2013-14 saw the side concede a mere 26 goals whilst their neighbours Real again let 38 goals past them.
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In 2012-13 saw a Real side led by Jose Mourinho concede 42 goals, ending the season a whopping 15 points behind champions Barcelona
The previous season saw the club's best defensive display since the mid-1990's as just 32 goals were conceded.
With such small margins separating the country's two biggest teams, conceding just several fewer goals over a season could well see the league title change hands.
Former Real academy goalkeeper Kiko Casilla has joined from Espanyol for a fee of €5 million [£4 million] after being released by the Madrid club in 2007.
The 28-year-old Catalonia international has been Espanyol's first choice 'keeper for the past two seasons and earned a call-up to the Spain side in 2014.
Danilo has also linked up with his Real Madrid teammates this month after signing the 24-year-old for £23 million back in April. Danilo joins from Porto having appeared 91 times for the Portuguese side, scoring an impressive 11 goals from his right back position.
The former Santos man is described as a quick, technical player that can provide a big threat going forward.
Through Danilo's arrival at the Bernabeu, the option is there for Alvaro Arbeloa to leave the club after a disappointing last campaign. Arbeloa, now 32, is rumoured to be a target of his former side Liverpool.
Defensive midfielder Casemiro (23) has returned to Real following the club activating a buy-back clause in his contract following a successful period on loan with Porto. The Brazilian has nine full international caps to his name and is likely to act as a squad player, filling the gap left by Sami Khedira who's contract expired last month. Khedira has since signed a 4-year-deal with Juventus.
Barcelona have reacted to their own concerns in midfield by completing the signings of Arda Turan and Aleix Vidal for a combined total of €55 million [£38 million].