From that same article:
A microcosm of Pierzynski's approach was mentioned by more than one of the backstop's former teammates, who revealed his propensity to spend a significant amount of time looking at his phone while at his locker during games. In one instance, after a particularly rough outing in which the starting pitcher had been pulled early in the game, Pierzynski could be found staring at his phone while the pitcher gave off the appearance of being an emotional wreck just a few feet away. That incident paved the way for at least one complaint to management from a teammate.
The frustrations with Pierzynski among the Red Sox grew with the catcher's indifference toward the perceived needs of the club. While it was understood that former Sox catcher Jarrod Saltalamacchia had some flaws in his game, it was noted in multiple corners of the clubhouse that the difference between the current Marlins backstop and Pierzynski was that Saltalamacchia was invested in his pitchers' successes and failures, whereas Pierzynski had limited interest in branching out beyond himself.