ST. LOUIS — Ahead of the most pivotal stretch of his career as an MLB starter, Roki Sasaki had the idea to completely alter his signature pitch. During the Dodgers’ last road trip in late April, Sasaki navigated a 4 ⅔-inning, three-run outing against the Rockies at Coors Field. Like most of his starts this year, the results were underwhelming. Under the hood, however, he felt like he was finally making progress. Dodgers pitcher Roki Sasaki had better results in his last game against the Cubs. He will look to continue that Saturday against the host Cardinals. AP Thus, when he sat down with Dodgers pitching coaches later during that trip in San Francisco, the right-handed phenom expressed confidence with the state of his mechanics –– then suggested an idea about how to improve his inconsistent arsenal.…