But for manager Joe Maddon, the changes that have gone on inside Upton's head over the past year are important, too.
"B.J.'s really grown up a lot over the last year or two," Maddon said. "He's got a different way -- a more professional way -- about him. And he's getting it. He's just getting it.
"He knows that as he goes, we can go. But the thing about B.J. that's great is that he likes that responsibility. He's not going to shy away from it. We have some guys that don't mind being in the center of attention."
Last season, Maddon had to discipline the young player twice for showing a lack of hustle. Upton was benched twice in August for not running out a grounder in the first instance, and a double-play ball in the second.
"We've got some guys and they're still learning how to be big league baseball players here," Maddon said. "More than ever, this period in baseball, you've got to understand that there's a lot of guys still developing at the Major League level as Major League baseball players. They're not spending as much significant time in the Minor Leagues, so you're going to see some things that maybe you don't want to see. But then again, you have to be patient and keep putting the information out there until they get it."
In November, Upton underwent surgery to repair a torn labrum in his left shoulder, and did not make his season debut until April 13. He batted an anemic .177 over the month of April, with a .226 slugging percentage.
"Earlier on in the season, it didn't look that good," Maddon said. "B.J. was coming off his shoulder surgery and it just wasn't happening early on.
"He didn't even have Spring Training with us. He was there, but he didn't do anything. He couldn't. And so he's got this later, shorter version of Spring Training. And then he comes to us and you're expecting him to be getting right in the swing of things. I didn't expect that to necessarily be quick."
Despite Upton's struggles, Maddon kept the 24-year-old in the lineup and in the leadoff spot, confident that Upton would regain his form.
"You could see in your mind's eye that when it clicks, it could be really special, so for me, it was kind of easy to stay with it," Maddon said. "When people all of a sudden want to jump change, just try to understand who we're talking about here. It's not a 38- or 39- or 40-year-old guy at the back side of his career. This guy hasn't even reached his maximum potential yet, so when you have players like that, I think it's easier or more necessary to be patient."
Maddon's patience paid off, as Upton hit .324 in June, with a .562 slugging percentage and 14 stolen bases. It's an improvement Maddon chalks up to Upton's natural talent as well as his growing maturity as a player.
"I think last season in the playoffs when he really showed people what he was doing [was a turning point]. I think this year, how he handled the adversity, also showed that he's turning a corner, too," Maddon said. "He got frustrated a couple of times, but never made it visible out here.
"The phrase I would often use is that as long as he doesn't give up on himself, I'm not going to give up on him. And he never gave up on himself, which I also think is a sign of maturity."
Erika Gilbert is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.