All those extra games, of course.
"We're fortunate enough that we get to play baseball every day," Moustakas said. "But when you're playing 162 in a row, your body starts to get a little tired. You just learn how to prepare yourself better for games, do this and do that. You start to learn about the right way to approach things. With this group of guys we've got in here, it's easy to figure it out. They help us out a lot, the veteran guys do."
The 24-year-old might not be in that veteran group yet, but he's already one of the Royals' most recognizable players. That speaks both to the young roster and the impact Moustakas has made in his brief time as a big leaguer.
Called up on June 10, 2011, Moustakas struggled initially. With a strong finish in his rookie year, he hit .263 with five home runs and 30 RBIs in 89 games.
Fast forward a year, and Moustakas was one of the brightest spots of the Royals' 2012 season. He's among many of the returning players -- along with newcomers such as pitcher James Shields -- who are scheduled to appear at the Royals FanFest on Saturday, Jan. 19, at the Overland Park Convention Center.
Moustakas finished 2012 with 20 home runs and 73 RBIs, both of which ranked second on the team behind designated hitter Billy Butler. His 34 doubles trailed only Major League leader Alex Gordon's 51. While Moose saw dips in his batting average and on-base percentage from last year, his slugging percentage jumped up from .367 to .412, and he raised his OPS from .675 to .709.
But it wasn't just an improvement at the plate. Moustakas' efforts to improve his defense were well-documented, as he worked with several coaches, namely Royals infield coach Eddie Rodriguez. The hard work paid off. Moustakas was sensational at the hot corner, making tough plays look routine and stopping nearly everything that came his way. At one point, he went 47 consecutive games without an error, and his 41 double plays obliterated the old club record of 34 set by Mark Teahen in 2006.
"A lot of people forget I got drafted in the first round as a shortstop, so I did have the ability to play over there. I was able to make plays. But it was a lot of work moving over to third base," Moustakas said. "Eddie Rodriguez helped me a lot, and [former Minor League infield coordinator] Mark Harris helped me out a ton. Learning from all these great guys that we have around here, [including] George Brett, being able to work with those guys helped me out tremendously.
"The more ground balls you take, obviously, the better you're going to get. Being able to have the guys out there that will hit me ground balls every day, come out there and work with me every day is really a blessing."
Right from Day 1, though, whether the bat or the glove or both were going to impress, Moustakas had already cemented himself as a fan favorite in Kansas City. A play at third on Opening Day was greeted with the now famous Moose calls, which followed him all season long.
By late spring, foam Moose antlers were available for purchase in the Royals' gift shop. And later in the year, the Royals offered Moose antlers as a promotional giveaway.
Moustakas said he has a few sets of those, which he planned to distribute to his family in California. He wouldn't wear them, he said. But don't think he's not enjoying the attention.
"I just kind of go out there and play the game, and whatever happens happens. But it's really cool to be able to go out there every day and listen to those fans cheer for you. It gives you a little extra boost," he said.
It's that kind of modesty and hard-working attitude that won fans over in the first place. And it's really there, anchoring how he thinks after two seasons in the Majors.
"My evaluation of myself is solely based on the team's performance, so whatever we end up doing as a team, that's how I look at myself," Moustakas said. "I don't really look at personal numbers or any individual numbers. This is such a team game and such a team sport, you start looking at that stuff that's when you start going really downhill. So I try to make sure it's always about getting those W's first, and that's the category I look at at the end of the year."
The fans aren't the only ones impressed with his performance last season.
"He had a phenomenal season," first baseman Eric Hosmer said. "Twenty home runs and 80 RBIs or whatever it is, he came to play. And his defense -- I saw him for a lot of years in the Minor Leagues and I've seen how good he can be. I think everyone in KC really saw how good he is defensively this year."
According to manager Ned Yost, though, no one has seen Moustakas' full potential quite yet.
"Look, if you're looking for the finished product, that ain't going to happen," Yost said. "He improved greatly all season long, defensively, offensively. But he's still just scratching the surface of what he's going to be able to do. I think when it's all said and done, he's going to be a consistent .275, 25-to-30 [home runs], 100 RBIs with great defense."
If Yost's prognostications are correct, Kansas City fans will be mighty pleased.
Vinnie Duber is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.