These ratings are given to players based on their performance during the 2014-15 season and range from A+ (the best) to F (the worst). They are given based on how well they performed the role they were given, so they are not absolute but relative to expectation.
Pique proved, once again, that he is one of the best defenders, if not the absolute best, in the world. His dominance in the air helped Barcelona turn a weakness into a strength, and once again he was elegant on the ball. He even made some timely sliding tackles and blocks. He did have a few wobbles through the season, to be fair. There was a point in which he struggled for form but Luis Enrique wisely benched him and aided him to gain composure. However, going towards the business end of the season he - like Daniel Alves - really turned it up and put in masterclass after masterclass. His lone blunder was a poor pass that allowed Sevilla to equalize in the dying minutes. But he quickly tweeted he was sorry and that they would improve. And here we are. His growth as a leader has been immense after the departure of Carles Puyol.
With the signings of Jeremy Mathieu and Thomas Vermaelen, plus the development of Marc Bartra and the sale of Alex Song, there were good indications that Mascherano would spend more time as a defensive midfielder than a centerback. However, with Sergio Busquets on the team, this would mean he'd be pushed out of the starting XI. Put frankly, el Jefecito is just too damn good for the bench. Lucho tried to make it fit with weird formations before settling on putting Mascherano back in central defense. And man, did he earn it. His tackling ability is basically unparalleled, and despite being much shorter than most centerbacks, he holds his own in the air. It's hard to think of him having a truly bad game, and his fiery personality is a welcome addition. His showings in midfield proved there's a gap between him and Busquets in the Barcelona system, but he did an okay job. Sometimes he was uncharacteristically nervous, like in the opening stages of the Champions League final, but in reality he rarely made a mistake.
Mathieu came to the club in a divisive transfer. Put simply, Mathieu is not a star name nor a huge prospect, just a solid veteran. The issue is at around 20 million euro, Valencia didn't let him go cheap. However, opinions on him being a poor transfer changed as the season went on. He didn't project calmness as much as Pique or Mascherano typically did, but he was also not particularly error prone, despite his reputation. More than that, Mathieu was dominant in the air, and actually did a fair bit on the ball. He was fairly confident in joining the attack, and scored two hugely important goals just when Barcelona most needed it - one against Real Madrid in a 2-1 win and another against Celta in a 1-0 win.
With Pique, Mascherano and Mathieu deservedly logging significant minutes, Marc Bartra mainly was used in the less glamorous matches. That said, Bartra made use of his time on the pitch and usually gave a good account of himself. Even in his most difficult game, against Paris Saint-Germain in the Champions League, Bartra seemed more than up to the task. Positionally, he has had some poor moments on occasion but even those are becoming more of a memory. Confident on the ball and good without it, Bartra's real problem, it seems, was merely a lack of playing time. Partly this is because of the quality ahead of him, but partly next season Luis Enrique hopes Bartra can make an even stronger case for himself to start unseating Mathieu and Mascherano more often in big games.
Vermaelen was injured most of the season, though encouragingly, he was good in the only match he played all season.
No grade, incomplete
Ie made his senior debut in the Copa del Rey. Not much to say about him yet...
No grade, incomplete
Worth mentioning that Bartra in particular tended to play easier matches, but even still, his stats are very impressive. Mathieu's stats also look good. This reinforces the idea that Barcelona has plenty of good talent at CB, especially with Vermaelen returning to fitness.