Upton has matured, too, and he has come to understand what was expected of him. He had to learn on the job because the Rays rushed him to the Major Leagues and watched him grow dramatically through the years.
In 2012, only Mike Trout had a better combination of speed and power among American League players. Upton has made it look routine, averaging 18 home runs, 33 doubles and 39 stolen bases the past five seasons.
Upton is not perfect. Let's be upfront about that. He's not nearly the center fielder Michael Bourn is, and he has averaged 156 strikeouts the last five seasons. Upton also seems to lose focus at times, and there have been games when he didn't seem to be playing as hard as he should have.
One problem with making a judgment about Upton's effort is that he has such a long, smooth stride that he doesn't appear to be running hard, even when he is. Regardless, those instances were reduced dramatically this season. Rays manager Joe Maddon sensed a more mature Upton early in Spring Training and watched it carry right through the season.
Even with Upton approaching his 1,000th game in the Major Leagues, he may have his best baseball in front of him. Down the stretch last season, as Upton delivered big moment after big moment, Maddon was effusive in his praise.
Upton's path to the big leagues wasn't smooth. Tampa Bay made him the second pick of the 2002 First Year Player Draft and had him in the Major Leagues two years later.
Upton was 19 at the time and not ready. That decision seemed more about marketing than baseball, and even though Upton didn't return for good until 2006, he was never allowed to grow and develop with the methodical path up the development ladder.
So some of that growth and development came in the Major Leagues, and it didn't come without some pain. Upton had wild swings of inconsistency, and sometimes frustrated almost everyone.
Through it all, Upton produced. The Rays appreciated that he loved the game and that his competitive fires raged most of the time. There may have been times last season when Upton tried to do too much to compensate for Evan Longoria's absence, but he clearly was all in.
Once Longoria returned in August, Upton put together a monstrous finish, with 18 home runs and 33 extra-base hits in 54 games.
Upton seems a natural fit for the Braves, who were unsure about their ability to re-sign Bourn. During a recruiting trip two weeks ago, Upton impressed almost everyone from general manager Frank Wren to manager Fredi Gonzalez to former manager Bobby Cox with his demeanor and commitment to help the Braves win another championship.
Upton will fit in nicely with a low-key clubhouse built on professionalism and the expectation of winning. He had those things with the Rays, too, so the adjustment will not be dramatic.
As far as the expectations that come with signing the largest contract -- $75 million over five years -- the Braves have given a player, Upton should be fine with that. Baseball's marketplace is changing dramatically as revenues pour in, so the standards are changing, too.
Upton has lived with large expectations from the moment he played his first Major League game. He was always expected to be the next great thing, and so $75 million simply is the next step along the way.
Upton is one of those players the Braves like now, and probably will like even more after he has joined them. He has enormous skills and the desire to be great. Upton is also not without some flaws, but every other player has one or two as well. Once Wren realized that agent Scott Boras seemed likely to take Bourn on a potentially drawn-out odyssey through free agency, he acted quickly to fill the hole in his lineup. He won't regret it.
Richard Justice is a columnist for MLB.com. Read his blog, Justice4U. This story was not subject to the approval of Major League Baseball or its clubs.