SportMatrix also suggests that Dani does more wrong than most other fullbacks in the discussion of the top tier - coming in second, behind only Real Madrid's Danilo. This is where the polarizing opinions come in. While Dani does a lot right, he also does a lot wrong - and the difference between his good and bad actions ranks just outside the top 10. And when we flip to offense, his rate of "good crosses" isn't great, either. While he completes a lot of them, his rate of good crosses is just inside the top 10.
To be clear, none of this suggests that Dani isn't a good player. Everything available suggests that he's still a top 10 right back in Europe - potentially even top 5. While he is polarizing, his rate of doing things well is really good - which gives him a decent cushion. The only concern is the effect that has on the rest of the players. Dani's great moments help players like Messi, Suarez, and Neymar score, but his bad moments force Rakitic, Pique, and Busquets to make up for his mistakes - which often leaves the defense open and vulnerable.
His mistakes go far beyond one step, and can often result in a chain of events leading to a goal allowed by another player. Much of Rakitic's first few months with the club were spent playing out of position on the right flank because Alves wouldn't (or couldn't) - and his performance suffered because of it. Dani's poor performance has a tendency to permeate throughout the rest of the squad, and can cause the team to struggle mightily, at times.
The highs are definitely high with Alves, but the lows are also very low - and that creates both polarizing opinions and performances. Dani's become one of the few guys that can create levels of opinions - on both ends - as extreme as they come. The inclusion of Aleix Vidal in the squad should help the club find a more consistent performer, and that should help the club tremendously, but for now we just have to hope that his high stays high - and we can avoid any miscues.