Every year, a handful of MLB players get really, really lucky.
A few extra seeing-eye ground balls get through the infield and a hitter best suited to benchwarming looks like a legitimate big-league starter.
A good-not-great pitcher benefits from an unusually skilled backing defense and suddenly finds his name popping up in the same sentence as Cy Young.
One of the greatest innovations of sabermetrics is the ability to measure and isolate the element of luck in players' performances (at least, to some extent).
As we count down the days until the start of the 2011 MLB season, we can use these new techniques to identify who amongst last season's stars is unlikely to maintain a high level of performance this year.
So, who was the luckiest player in the game last season?
There's no way to know for sure, but there is no doubt that one of the flukiest hitters in baseball last year was a rookie center fielder named Austin Jackson.
The Detroit Tigers got a lot of flack when they traded Curtis Granderson last winter, but they seemingly redeemed themselves when Jackson, the prospect they traded for to replace Granderson, finished second in the AL Rookie of the Year voting and made a name for himself as a player to watch for years to come.
In his debut season, Jackson hit .293 with 103 runs, 27 steals and a 3.8 WAR—solid numbers for any player, let alone a 23-year-old with zero previous big-league experience.
The problem is, Jackson doesn't profile as a strong contact hitter. His seven percent walk rate indicates below-average plate discipline and his unsightly 27.5 percent strikeout rate puts him at the 10th percentile for MLB hitters.
How did Jackson pull it off?
His saving grace was his .396 batting average on balls in play, the highest in the game and 99 points above the league average of .297.
Batters have some control over their hit rates, and Jackson is the kind of player who could sustain a high BABIP. He makes good contact (24.2 percent line-drive rate, tied for the best in the league) and speedy ground-ball hitters collect more hits than their slower-footed peers.
But there's a difference between a high hit rate and an absurd one. His .355 expected BABIP reflects his impressive batted-ball profile and wheels, suggesting he will continue to leg out more than his fair share of hits.
But .355 is still a long way from .396. Plug his xBABIP in for his BABIP and, making the simplifying yet generous assumption that every hit he'd lose would be a single, his 2010 slash line falls to .264/.311/.370.
With a below-average OBP, he would have fewer chances to steal bases and score runs, which would drag his value down even further.
Accounting for the extra-base hits he would have lost by looking at the proportions of his hits that went for doubles and triples, his slugging percentage drops to just .337.
Yes, that puts his slash line at .264/.311/.337.
A guy with a .648 OPS isn't a Rookie of the Year candidate. With that kind of production, he'd have trouble just finding a job.
Moreover, his high xBABIP is based largely on his exceptional line-drive rate. If he can't keep that up, things could get really ugly.
That's not to say Jackson is a worthless player. His good defense still gives him value (at least, in the real world—not so much in fantasy). Plus, he's only 24 and has plenty of time to continue to improve.
Still, even if he takes a step forward as a player in 2011, you should expect a big regression in his back-of-the-baseball-card stats.