By day, Rick Porcello builds up core and legs, strengthens his arm and hones his pitches. By night, the Red Sox starter puts in work on his mind. On Porcello’s nightstand in his temporary southwest Florida home sits Harvey Dorfman’s “The Mental ABC’s of Pitching,” a bible for pitchers since publication in 2000 by the late pioneer of baseball sports psychology. It had been eight years since Porcello last read the book, but this spring he dedicated himself to a thorough, page-by-page reread. It’s been a struggle at times, Porcello admitted with a sheepish grin recently, to keep his eyes open for too long, but “I’m working through it.” He gave himself no choice. Porcello, who pitched a simulated game yesterday, followed up his nearly flawless 2016 AL Cy Young campaign with a season in which he was pounded hard nearly from start to finish. Last season, he led the American League in hits allowed (236) and the majors in home runs allowed (38). He wasn’t hurt (he did top 200 innings), and Porcello, one of the more thoughtful and intelligent pitchers in the game, understood as soon as the season ended that he had to change. And while working on his command of the strike zone and regaining trust in his sinker and feel for his changeup are keys to returning to 2016 form, Porcello knows his body did not operate in isolation from his brain. He knows altering his mental approach must take priority.