ST. LOUIS — Josh Naylor got to trot a lot Friday night, and that was very good news for the Mariners in their 3-2 victory over the Cardinals before 31,304 at Busch Stadium. Furthering distancing himself from the worst slump of his career to begin a season, Naylor belted the go-ahead home run in the sixth inning off St. Louis starter Andre Pallante, a no-doubt line-drive blast out to right field. It was his third homer of the season, measured at 107.3 mph off the bat and 418 feet in projected distance, and it came a game after he delivered a walkoff single in a 5-4 win over the Athletics on Wednesday. It also gave the Mariners a much-needed jolt to begin a six-game Midwest road trip. They had lost eight of their first nine road games to begin the season. “Getting that first one on the road is really important to set the tone for the series,” Naylor said. “The guys did a great job today through and through —offense and defense, pitching, baserunning.…