With Bayern Munich around the corner, the coach rested Lewandowski, Dembele and Pedri, among others. But the team needed them in the second half.
They came on shortly after Frenkie de Jong broke the scoring, in the 55th minute after a drab first half.
Raphinha hit the post early on. But there wasn’t much else to write home about for Barcelona, with Cadiz predictably sitting deep.
Ferran Torres, quiet, curled over before half-time while Memphis Depay struggled to get involved too.
Only Alejandro Balde really impressed, and should have earned a penalty when he was hauled down inside the box but inexplicably nothing was awarded.
The goal came when Raphinha played a brilliant pass to Gavi, whose cross was deflected into De Jong’s pass and he tucked home from close range.
On came the subs, who were already prepared, and the game was quickly swept from Cadiz’s reach.
Robert Lewandowski slid home after more good work by Raphinha.
There was an unfortunate pause of over 50 minutes for a fan with a serious medical issue to be treated and taken to hospital, before the game resumed.
Ansu Fati scored the easiest goal of his life after superb work by Lewandowski and then Dembele bamboozled Cadiz before blasting home from the edge of the box; his footwork fooling goalkeeper Ledesma, who could not handle the strike and palmed it in.
Homework done, before the trip to Munich on Tuesday.