At this point in the season, this stuff isn't going to tell us all that much. The sample sizes are small, meaning a few hits going into one bucket or another, or a few swings going into one bucket or another, can still significantly affect what has already happened and also affect what these numbers might look like next week (particularly for occurrences with lower probabilities). And I'm not going particularly granular here, sticking with essentially three sets of data from Fangraphs that are pretty broad.
The data itself also has some limitations. Batted ball classifications aren't quite as clearly delineated as this stuff implies. I'm largely quoting Pitch F/X data for the strike zone, unless otherwise noted, which will certainly deviate from what a given umpire is calling in a particular game. What pitch types and velocities batters have faced so far obviously depends on the repertoires of the pitchers they've faced. And so on.
All that said, this is something that should be interesting to track at least what is happening during the season, as we can check in on how these evolve over the next few months. It certainly can help explain why a player's production looks like it does, though it may not be all that helpful in explaining the root causes, such as why a player is swinging less or more.
A few other preliminary comments:
The "universal rules" regarding batted ball type are pretty much limited to that infield fly balls are really bad and line drives are good. For some batters, ground balls are good while fly balls are bad (see, e.g., Micah Johnson) because they have speed, while the opposite is true for others (see, e.g., Adam LaRoche) because their fly balls leave the park.
Same thing for swing percentages. Some guys make a lot of contact but it doesn't result in much production. Some guys don't but are very productive. Some guys swing at a lot of pitches outside the zone but they make contact. Some guys don't.
Below are the MLB averages, as well as an explanation of the stats to which I refer. If you want to see the full stats for all these players, just go to the player's Fangraphs page.
Currently trying to make his way back from a poor start, he's seeing more four seam fastballs (47.6%) than he has in his career (40.1%). And those are coming at him at about a half MPH faster than in the past.
He already has two infield flyballs after having only three all of last season. Perhaps most importantly, he's just not getting infield hits this year. Those accounted for 12.2% of his ground balls in 2014 (29 in total), good for 5th overall in baseball. Thus far, he only has two accounting for 4.9%. Last season's percentage probably was near the upper end of what could be expected from him but 10% or so should be about where a player of his skill-set is. He's hitting the ball hard at a slightly lower rate but he's also hitting the ball softly at a lower rate, resulting in more medium hit balls.
He's pulling the ball less than he has since his age 26 season (when he became a good hitter) and hitting it more to center. Perhaps most importantly, his hard hit percentage is just 19.5%, well below his career average of 25.9%. Like Eaton, he's seeing markedly faster four seamers, 1 MPH quicker than last season.
Cabrera is an elite contact hitter and this season is no exception. Pitchers are attacking him in the zone more than in any prior season (51%) and he's responded by making contact at his highest percentage of swings in his career (95.9%). Overall, he's swinging at balls in the zone in line with his career averages but he's swinging outside the zone less than ever (27.5%).
Abreu has hit more ground balls this season (49.3%) than in 2014 (45.5%). His hard hit percentage is also down to 32.0% from 36.4%. Notably, though, he hasn't hit a single infield flyball.
Pitchers don't appear to be approaching him much differently in pitch selection, though he has seen an uptick in two seamers. While he's seeing more pitches inside the strike zone (44.6% vs. 40.3%, non-PItch F/X), it's happening later in the count. He's seen first pitch strikes 51% compared to 59.5% last season. He may be seeing more pitches in the strike zone because he's swinging less frequently (67.3% vs. 73.1%).
He's hitting a lot more ground balls (45.1% vs. 37.9%) and few fly balls (35.3% vs. 41.3%), which is not good for a power hitter. When he does hit fly balls, though, they're leaving the park (16.7%) at essentially his usual rate. His softly hit rate of 17.6% is well-elevated from his career rate of 12.3% and, commensurately, his hard hit rate is 31.4% versus 36.5% for his career.
LaRoche is making a lot less contact outside the zone than he has in his career (49.0% vs. 59.2%), although he's offering at them at about the same rate. His contact inside the zone is also down a bit, resulting in an overall contact rate of 73.2% versus 77.7% in his career.
In terms of pitch selection, the only notable difference is that he's seeing fewer sliders - though he is seeing a bit of an uptick in cutters. Considering those pitches tend to be closely related, this may just reflect the repertoires of the pitchers he's seen.
Last season, Garcia was rather poor at making contact outside the zone at just 44%. While still below his career average, he's up to 50.7% this year. More importantly, he's making more contact inside the zone (87.4%) than he has in his career (81.0%). While he's hitting fewer fly balls (17.9% vs. 24.0%) and they're leaving the park at a lower rate (8.3% vs. 14.9%), he's hitting a lot more line drives (29.9% vs. 20%). This has resulted in a rather low ISO of .080 but does have his batting average up to .322 with a .409 BABIP.
There isn't anything remarkable in the pitch selection against him. One trend that may be interesting to watch this season, though, is that he's offering a lot less against pitches outside the zone. This season's 30.7% is easily the lowest of any season and well-below his career rate of 37.2%. This may be a reaction to last season, when he saw his out of zone contact rate fall to a career low of 67.0% (career rate 71.7%). Not much has changed there in 2015 as his rate is 68.0%.
His fly ball rate is slightly below his career average but, more importantly, he hasn't hit any of them out of the park (career average is 8.1%). He also is hitting more infield fly balls. His six on the season means that 27.3% of his fly balls aren't reaching the outfield, contributing to his .236 BABIP.
Like Garcia, Gillaspie has seen fewer sliders this season (6.3% vs. 13.0%). He's swinging at a career high rate (52.1% vs. 47.6%), which continues a trend from his first season with the White Sox of significant increases in both in and out of zone swing. However, he's making a lot less contact than in 2014, where his solid season was bolstered by a 70.7% out of zone contact rate. This season it's just 61.4%. Coupled with an 86.3% in zone contact rate, his overall contact rate is down to 77.4% - well below his career 83.9%.
Gillaspie is pulling the ball at an extraordinary 58.3% (career 41.3%), resulting in significantly reduced contact to the other fields (20.8% vs. 33.5% to center; 20.8% vs. 24.6% to opposite field). His hard hit rate is 22.9% versus 29.5% for his career.
He's seeing a whole lot more fastballs than he ever has. The 46.6% four seamers is well above his prior full seasons and his career 35.6%. It's not hurting his contact rates, however. His 77.5% overall contact rate is easily above prior seasons and his career 67.1%. This is largely fueled by a pretty extraordinary (for him) in zone contact rate of 90.3% versus 77.4% career. Part of this can be attributed to seeing the highest percentage of pitches in the zone in his career (53.4% vs. 50.1%) even though he isn't offering quite as much at those than in the past.
Unfortunately for Flowers, this changed approach hasn't resulted in production. He's hitting a lot more fly balls - 45.7% versus his career 36.2% and 28.5% in 2014) - which should be a good thing for a guy with a career 17.1% HR/FB. However, it's just 6.3% this season. His line drive rate is 14.3% versus his career 19.4%, which largely explains why his softly hit rate is elevated (25.7% vs. 20.6%) while his hard hit rate is diminished (25.7% vs. 30.1%).
This rookie, of course, doesn't have anything with which to compare other than league averages. As one might expect, pitchers are testing whether he can hit major league velocity. He's seeing four seamers 49.8% of the time, while the rest of baseball sees 35.8%. His swing rates are not particularly remarkable, as they're largely right at league averages. He does, however, swing a bit more outside the zone (32.2% vs. 29.9%), though this may be playing to a strength considering he's making contact on those pitches at a well-above average rate (72.9% vs. 63.8%)
His 54.3% ground ball rate also plays to his strengths, most notably seen in his 16.0% infield hit rate and his .360 BABIP. As one would expect, at 17.6%, he doesn't hit the ball hard very often. He's doing a decent job of using all fields with 37.3% of his batted balls going to both left and right fields with (obviously) the remaining 25.5% going to center.