To watch Roenis Elias efficiently dismantle the Detroit Tigers was to watch the development of a young pitcher. Elias was close to untouchable against the Tigers. He pitched the first shutout of his career — and the first by a Mariners rookie since Freddy Garcia in 1999 — in Seattle’s 4-0 win Sunday. But it was more than just the results. Elias baffled the Tigers in large part because his changeup was so effective. “I thought his changeup was the equalizer,” Mariners manager Lloyd McClendon said. Elias was primarily a fastball and curveball pitcher early in his career. But he realized that most of baseball’s successful pitchers had a changeup in their arsenal and decided he needed one, too. He only started throwing a changeup a year ago, and he struggled to control it then. But against one of the best lineups in baseball, the 25-year-old Elias turned to his changeup again and again. And Detroit never could get a good read on it. McClendon called the pitch “exceptional.” Catcher Mike Zunino said it was the best he has seen Elias throw his changeup. Elias agreed. Elias throws his changeup with the same grip as Mariners ace Felix Hernandez, who has given Elias pointers with the pitch. “Felix has refined it,” Elias said. The Tigers barely even dinged Elias. He gave up just three hits. He didn’t give up any hits to Detroit’s three best hitters: Ian Kinsler, Victor Martinez and Miguel Cabrera, one of the best hitters in the world. Elias never allowed a runner to reach second base. He stumped the Tigers by locating his pitches, which he has struggled with at times. The stuff has always been there. That has been clear from his first major-league starts this season. But Elias did two things he hasn’t always done in his brief career. He was efficient and threw all three of his pitches for strikes. The Tigers couldn’t sit on any one pitch. They had to be ready for all three. “His stuff is as good as any lefty in the league,” McClendon said. “He’s got quality, quality stuff. If he throws strikes, he’s usually going to be around late in the ballgame.”