NEW BRITAIN, Conn. -- After learning of his promotion, after just one hour of sleep, after two flights that took him from sunny Florida to upstate New York, and after an 0-for-2 debut with the Binghamton Mets, Brandon Nimmo learned that, yes, this really is a step closer to the big leagues.

The 21-year-old outfielder was packing his bag, readying to embark on a five-hour bus ride to Bowie, Md., one night last month when strength and conditioning coach Jason Griffin told him he could just leave it at his locker. Here, in Double-A, Nimmo and his teammates don't have to carry their own bags.

"I was like, 'Dang, all right, this is nice, this is nice,'" Nimmo said this week, still beaming at the realization. "Just leave it right in front of your locker and they take it on the bus.

"It's just a little thing. As you move up, you get pampered a little bit more. It's nice that the focus is for you to be able to focus on the game and not the outside stuff. It's the little things that make a difference."

That's life for Nimmo now. After he handled Florida State League pitching with ease during the first half, the organization gave him a midseason promotion for the first time since 2011, bumping him up to Binghamton from Class A Advanced St. Lucie. At an age when many are getting ready for their senior year of college -- or just beginning their professional careers, if they were selected in the First-Year Player Draft -- Nimmo has reached the second-highest rung on the Minor League ladder.

Nimmo has carried with him the hype of a first-round Draft pick since the Mets made him the 13th overall selection in the 2011 Draft, and that has followed him everywhere he's been. On Monday night, it manifested itself in the form of autograph seekers, all of whom left with smiles that had little to do with the 8-3 B-Mets win. Nimmo filled every request after a 4:30 a.m. arrival in New Britain and a 1-for-5 day at the plate.

"I'm enjoying it up here," Nimmo said. "It's a new level, but I'm excited for what it has to teach me. ... It's still baseball. It's very, very minute changes. Just looking to learn from it and keep adjusting."

So far, the adjusting hasn't come as easy as the equipment maintenance. Nimmo is hitting .179 with a .333 on-base percentage and .282 slugging mark through his first dozen Double-A games, a far cry from the .322/.448/.458 slash line he posted with St. Lucie that earned him FSL All-Star honors. He is still on pace to set career highs in most offensive categories, all of it coming against the best pitching he's seen as a pro.

Nimmo has cut down on his strikeout rate, too, from 131 times in 110 games last season to fewer than once per game with St. Lucie. More importantly, maybe, he walked nearly as many times (50) as he fanned (51).

The early Double-A struggles can be attributed to a number of factors. It's standard for a prospect to take time to adjust to a new league, especially when the players in that league are, on average, more than three years older than you, as they are in Nimmo's case. Eastern League pitchers overall execute their offerings with more regularity than their FSL counterparts, Nimmo has found, and only this week has he felt like he's truly found a new daily routine. Nimmo also pointed to better relievers and more refined defenses.

But then, with a pat of his chest and a knowing smile on his face, Nimmo added one more reason.

"It's pretty much been me," Nimmo said. "Normally I don't miss mistakes a lot, and when I'm not doing well, I'll miss mistakes sometimes. Maybe I'll foul them straight back or something like that. That's been one of the things that I've been able to notice. When I'm going well, I'll usually take as many swings as I do have at-bats."

For Nimmo, who ranks fourth among Mets prospects and second among the position players, according to MLB.com, it's more likely than not a matter of when -- not if -- he makes the adjustment to Double-A.

Hitting coach Luis Rivera has already seen immense growth after working with Nimmo in past years when he served as the short-season hitting coordinator.

"He's a totally different player from when I saw him when he was a rookie guy. He's more mature, stronger," Rivera said. "He needs to be a little more aggressive at the plate and he'll be fine."

According to Nimmo, who is a center fielder by trade but has dabbled in left with Binghamton, his most significant stride this season has been his range in the outfield. He said instead of watching the ball until he fields it, he'll read it off the bat, put his head down, sprint to "a spot" and pick it up again. This allows him to cover more ground quickly and forces him to get better reads.

"It's something I hadn't really trusted myself with before," Nimmo said. "Right off the bat, you need to have an idea of where that ball is going to end up, and that just comes from repetition, repetition, just practicing. That's the one thing we emphasized on in Spring Training they said they'd like me to work on, and I did, and it kind of just clicked with me. I've been able to put it into play a lot."

Given his ascent so far, and his apparent breakout season at the plate, those outfield strides could very well come at Citi Field sometime during the 2015 season.

"It's nice to get affirmation that you're doing things right," Nimmo said. "That brought another level of excitingness for me, and even more motivation."