One year ago, Trey Mancini was a prospect at first base and uncertain whether the 25-man roster could hold him on opening day. Chris Davis blocked him at his natural position, Mark Trumbo was ticketed for designated hitter duties and organizational debate centered on the wisdom of his part-time role in the majors versus regular at-bats in Triple-A. There’s been a dramatic shift as the Orioles near another spring training. Mancini is one of the certainties on a roster that still requires scaffolding in the construction phase. No one knows who’s starting in right field or behind the plate, who’s filling the last three spots in the rotation and joining Richard Bleier in left-handed relief, who’s replacing Ryan Flaherty as utility infielder. It wasn’t until Saturday’s FanFest that confirmation came of Manny Machado’s switch to shortstop and Tim Beckham’s move to third base. Mancini is a lock. He’s the left fielder, but he denies it in order to push himself to a higher level. “Every spring training I’ve gone in with the mindset that I’m fighting for a job and I’m not going to change that, no matter what the circumstances,” he said. “I’m kind of like a creature of habit in that regard, so I’m always going to go in trying to compete for a spot.” It’s accurate to portray Mancini as the heavy favorite after he batted .293/.338/.488 with 26 doubles, four triples, 24 home runs and 78 RBIs in 147 games and placed third in American League Rookie of the Year voting. He posted identical .293 averages against right-handers and left-handers, and he hit .301/.328/.398 in his final 28 games while the team collapsed around him.