By Nick Selbe Seattle nearly made the postseason last year with an abysmal offense. Now its lineup is raking and still getting better. View the original article to see embedded media. Welcome to The Opener, where every weekday morning during the regular season you’ll get a fresh, topical story to start your day from one of SI.com’s MLB writers. On Sunday, Mariners rookie Julio Rodríguez did something remarkable: He hit a home run. The three-run blast was notable not only because it was the first in the highly-touted rookie’s big-league career, but because it gave Seattle a 5–0 lead over the Ma…