This has been four years in the making for Green, drafted out of college as a shortstop in 2009 before embarking on a somewhat lengthy journey to the Majors, playing six different positions along the way while his employers debated the best fit. He has finally found a home at second base.
"I feel really comfortable there," said Green, ranked by MLB.com as the A's No. 3 prospect, before Monday's game. "It's kind of just second nature now. Being able to play there pretty much every day the last couple of weeks has really helped.
"It's a move I'm OK with now. It was kind of mind-boggling at first with all the position changes, but they always said it was for the better in the long run, and it's definitely worked out."
The plan is for Green to platoon with Eric Sogard at second, getting starts against left-handed pitching -- a move that finally brings permanency to Jed Lowrie's place at shortstop, his natural position. As for Lowrie's backup, manager Bob Melvin says that job belongs to Sogard.
Green, 25, was hitting .318 with a .374 on-base percentage, next to 11 home runs, 25 doubles and 49 RBIs in 81 games with Triple-A Sacramento.
"He's swinging the bat really well; he's had real good at-bats against left-handed pitching and is way more comfortable at [second base] now," Melvin said. "We just felt like the way he was playing at the time, it was the right time to get him here and get him the opportunity."
"It's a great feeling knowing that the organization and the people at the top feel comfortable in my ability to play this game at a high level," Green said. "Even when the team's playing very well, they're going to call me up and see what I got."
Green had most of his immediate family on hand for his debut in Pittsburgh, which includes dad Gregg, mom Valerie, brother Garett and sister-in-law Ashley, all from the Southern California area. He went 0-for-3 with two strikeouts in a 2-1 A's win.
They were his first call after he learned of his promotion from Sacramento manager Steve Scarsone on Sunday afternoon in Fresno, shortly before the River Cats were about to play a game. Green was scratched from the lineup and instead took a series of flights that led to his arrival in Pittsburgh about 9:30 a.m. on Monday.
"Scarsone called me in and said I was coming up here, and I just thought he was fooling around with me at first, just because that's his personality," he said. "He told me that's something he wouldn't fool around with. I thought he was joking at first, to be completely honest, and kind of just speechless. It definitely didn't really sink in until I told my mom and she started crying."
As for Rosales, who was hitting .200 on the season, his fourth in Oakland, the A's will have 10 days to trade, release or pass him through waivers.
"That was a tough decision, it was," Melvin said. "Adam has been here awhile; he can play different positions; he's versatile; he's a great teammate; he's loved by the players in the clubhouse. He's one of those guys you just always pull for. If he ends up with someone in the big leagues, great. If not and we can keep him in the organization, that'd be great, too."