Batting average on balls in play, or BABIP, is our best measurement of a player's luck (or lack thereof) throughout the course of a season. When we use the term luck, we only mean to suggest that, throughout the course of a player's career, he sees his BABIP occasionally soar over or under his career average, mostly as a result of chance.

Pitchers have essentially no control of batted balls in the field of play (with some exceptions such as knuckleballers), so this fluctuation in year-to-year BABIP can lead to some historically lucky and unlucky seasons. Batters tend to have more control over their average on batted balls in the field of play. Speedier hitters tend to beat out more ground balls and exhibit higher BABIPs (such as Carl Crawford's .327), while slower hitters tend to have lower BABIPs (such as Edwin Encarnacion's .273). For a pitcher, a season with a BABIP considerably lower than his career BABIP indicates a fairly "lucky" season, and for a hitter, a season with a BABIP considerably higher than his career BABIP indicates a fairly "lucky" season as well.

If we consider BABIP in terms of points (i.e. multiply it by 1000) rather than an average, and limit ourselves to players with well defined career BABIPs, we find that a hitter's BABIP has a sample standard deviation of 31.3 versus 21.1 for pitchers. This difference results from the existence of hitters who have characteristics making them more inclined to have higher or lower BABIPs, leading to a wider spread of data.

Let's go through the last five years of MLB seasons, finding the "luckiest" and "unluckiest" seasons based on deviations away from a player's career BABIP (in this case excluding 2014 data). For sake of being fairly sure of a player's actual long-run BABIP, let's limit ourselves to pitchers who have thrown at least 1,000 innings, and hitters with at least 2,000 plate appearances for their careers. Similarly, let's throw away shortened player seasons by considering pitching seasons of at least 150 innings pitched, and hitting seasons of at least 400 plate appearances. Over the last five years, there have been 281 such pitching seasons and 360 such hitting seasons.

The 10 Luckiest Pitching Seasons of the Last 5 Years

While taking nothing away from Justin Verlander's stellar 2011 AL Cy Young and MVP campaign, we note that his .236 BABIP was 52 points lower than his career BABIP at the time, resulting in a 2.40 ERA despite a higher 2.99 FIP. We also see that Ervin Santana's 2012 season could have been even worse had his season BABIP not negatively deviated from his career BABIP by such a large extent.

The 10 Unluckiest Pitching Seasons of the Last 5 Years

Justin Verlander, Max Scherzer, Randy Wolf, and James Shields all appear on both of these pitching lists. Interestingly, Derek Lowe appears twice on the list above, with two seasons in 2009 and 2011 in which high BABIPs inflated his ERAs despite respectable seasons.

As we've previously mentioned, a hitter is more in control of his BABIP than a pitcher is. But even for a hitter, a fair amount of luck is involved when he puts the ball in the field of play. Let's find the 10 luckiest and unluckiest hitting seasons of the last five years:

The 10 Luckiest Hitting Seasons of the Last 5 Years

Unlike our list of "lucky" pitchers, there really isn't a bad offensive season on this list, with the lowest wOBA being Omar Infante's .343 in 2010, which was still above the NL league average of .318.

The 10 Unluckiest Hitting Seasons of the Last 5 Years

Our list of "unluckiest" hitting seasons is topped by Aaron Hill's 2010 campaign, where he saw his average drop 81 points from his previous year, and his BABIP drop an astonishing 95 points below his career average. Ichiro, whose superb bat control and speed results in a career .344 BABIP, experienced a 49 point BABIP drop from his career norm in his final full season with the Mariners.

As we can see, even the most talented hitters and pitchers are susceptible to fluctuations in their BABIPs, causing some uncharacteristically great or terrible seasons.