An agreement was reached between the Mariners and agent Scott Boras about 15 minutes before the 9:01 p.m. PT signing deadline.
After spending a leisurely summer on the East Coast, "working out and enjoying my time off," Ackley was told on Monday afternoon to fly cross-country for a physical exam in Southern California.
"It was short notice, but I ended up getting it done, and it worked out for the best," he said. "I knew we must be pretty close, but I guess there was always a little doubt that something wasn't going to happen. I figured that by coming out [to California] and getting the physical and everything done, things were hopefully going to work themselves out.
"I was kind of hoping I wasn't flying all the way out to California and not signing. That would have been disappointing."
What was the final half-hour like?
"It definitely went down to the wire, and it was pretty nerve-wracking," he said. "I was just sitting there, and when you are not really talking at all and not hearing anything, you kind of wonder if things are going to get done. But I just had faith that things would work out. They did, and I'm happy about it."
Ackley returned home on Tuesday and will await word from the Mariners as to when he must report to the Instructional League in Peoria, Ariz. He also is expected to play for the Peoria Javelinas in the Arizona Fall League.
Though he played first base most of last season for the Tar Heels, Ackley is projected to become an outfielder for the Mariners, and he said that because of his speed and ability to run down balls, he believes the outfield is the best spot for him going forward.
"But I'll play wherever the team needs me," he said.
The Mariners had one opening on their 40-man roster, and filling it with Ackley was critical in the deal being finalized.
"It was real important," Ackley said. "I mean, any time you have an opportunity to be on a Major League roster is a big thing. I can't even imagine being picked this high [second overall] in the Draft. This has all been so exciting, and I don't think it has sunk in yet."
Just as general manager Jack Zduriencik hasn't given a timetable for the sweet-swinging left-handed hitter to make his Major League debut, neither does Ackley.
"I really don't know long it's going to take," Ackley said. "I know it's going to take a lot of hard work. I think when I get there is out of my hands. That's up to the organization to decide, and it's up to me to put myself in a good position by working as hard as I can and leave it up to them for when I get there."
The last time Ackley played was at the College World Series, in June.
"I have been working out and just enjoying my time off," he said. "I have stayed in baseball shape and tried not to lose anything, but I had a long season. It has been a pretty long grind, and now I'm getting ready for a chance to play professional baseball. It is a challenge I have been waiting for."
And the Mariners are thrilled about giving him that opportunity.