Baseball is hard.
It's difficult enough to have a successful year in the majors without some dude on the Internet chalking the performance up to batted ball luck, park factors and other caveats, but that's the world we live in. Fortunately, those sorts of things can help us -- and more importantly, key people in major league front offices -- predict players who are candidates for improvement, and on the flip side, ones who might be in for a rough year.
Michael Cuddyer, Mets
From a counting stats perspective, it's going to be hard for Cuddyer to put up the kind of numbers in New York that he did during the past two seasons in Denver. In 2013 and 2014, Cuddyer benefited from a batting average on balls in play nearly 70 and 40 points higher than his career norm. He didn't hit a ton of home runs in Colorado, but Cuddyer took advantage of a spacious outfield to drop in extra-base hits at career-best rates.
Citi Field has a large outfield, but it's not quite as big as it used to be after a couple of instances of the fences being moved in. Cuddyer isn't likely to improve upon his home run power as he gets older, so he's going to have to hope he can find gaps. That won't be quite as easy in Queens as it was in the Mile High City.
Nelson Cruz, Mariners
Cruz hit a lot of home runs last year playing half of his games at a park that, for the first time in recent memory, didn't yield them at a well-above-average rate. In that sense, a simple ballpark change might not affect Cruz as much as it likely will a player like Cuddyer. Plus, his strikeout and walk rates were better last year than they had been since 2010. But he's likely going to have a hard time repeating a 17.3 percent HR/FB rate at that park, at his age and in a non-contract year.
He's not going to fall completely off a cliff in 2015, but chances are the beginning stages of a natural decline are in the works for the 34-year-old Cruz.
Josh Harrison, Pirates
What happens when a player outperforms his career BABIP by more than 75 points? Usually, a breakout season, which is what Harrison had last year when he finished with a .315/.347/.490 line, blowing his past production out of the water. Harrison never had more than 276 plate appearances in a season prior to 2014, so there's a chance that some things -- such as his BABIP -- began to normalize (for the better) in a larger sample size. It's not likely that he'll be so lucky going forward, though. And that's a problem considering his career 3.3 percent walk rate.
Harrison played six different positions last season and handled them all well. He's a valuable player for a contender to have on a roster, but despite his tremendous 2014 season, he still might not be an everyday player. We'll know more about him after what very well could be a down year in 2015.
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Phil Hughes, Twins
Hughes walked 16 -- sixteen -- batters in more than 200 innings of work last season. Sure, he's not afraid to throw strikes because of the extent that his new home park limits offense. But in a normal year, it wouldn't be surprising to see Hughes walk at least double that many batters purely by accident.
His 2.65 FIP last season was more than a run and a half lower than his career average up to that point. It's possible that, with the low walk and relatively high strikeout rates, Hughes' FIP will remain strong. But he gives up a lot of contact, and if his home run rate (1.9 percent last year, 3.1 percent for his career) normalizes, he could be in some trouble.
Masahiro Tanaka, Yankees
There's not a lot of data supporting an assertion that Tanaka was overly lucky in his rookie season and that he won't be as good going forward, so he's a bit different than the other players on this list. Really, the reason Tanaka could be a bust in 2015 is because how can he possibly be as good as he was last year? The 26-year-old right-hander struck out 141 batters and walked only 26 in 136⅓ innings.
Even a small letdown would still allow Tanaka to be one of the best pitchers in the league, but a not-insignificant injury combined with hitters making their usual adjustments might result in at least moderate negative regression. That said, Tanaka still looks like a great pitcher and, provided he's healthy, should remain that way for years. He just might not be historically dominant like he was in 2014 going forward.
Adam Wainwright, Cardinals
Even before Wainwright's recent abdomen injury, there was a good chance of him hitting a wall in his age 33 season. As noted in the Baseball Prospectus annual, Wainwright had little shot of improving upon, or even sustaining, his production from last season. In fact, his 25 percent chance of a "collapse" is one of the highest among established pitchers in the league.
Add the injury, and Wainwright appears destined for a down year. Like most of the other players mentioned above, a significant downturn in production is only possible because the bar was set so high to begin with. But Wainwright over the last two years has pitched more innings than just about anyone else in baseball, a trend awfully similar to the one that led to him missing the entire 2011 season.