At the time of this writing, there are 37 major league hitters with a wRC+ of 150 or higher. There are the usual suspects: Bryce Harper, Mike Trout, and Nolan Arenado are on the leaderboard to no one’s surprise. There are exciting young prospects, including Mitch Haniger, Aaron Judge, and Joey Gallo. Then there are unexpected names like Eric Thames, Cesar Hernandez, and Robbie Grossman.

Lengthy articles could be, and have been, written about any of the players above. One player who hasn’t received much publicity despite some relatively prolonged success is Grossman.

He checks in with a 158 wRC+ in 67 plate appearances so far this year. Steamer projects a .322 wOBA and 99 wRC+ for the rest of the season (ROS), and that projection puts him just a few ticks behind his highly-touted teammate Max Kepler. Although Kepler is three years younger and may have a higher ceiling, the point is that name recognition can play a pretty big role in how we analyze players.

Also, Grossman used to be bad. From 2013 to 2015, he had just a .281 wOBA and 77 wRC+ in 202 plate appearances against left-handed pitching, despite being a switch hitter. Since 2016, however, Grossman has a .417 wOBA and 166 wRC+ in 170 plate appearances against lefties. Even with his early-career struggles against lefties, Grossman now has a lifetime .344 wOBA and 118 wRC+ against them.

Since 2016 against all pitchers, Grossman has amassed 452 plate appearances spanning 113 games and has hit .283/.398/.444 with a .369 wOBA and 133 wRC+ (these numbers are excluding results from Monday). He boasts a respectable .327 wOBA and 107 wRC+ in just over 1,200 career plate appearances.

What’s behind Grossman’s newfound success? The first place to look is his swing. Did anything change from his time in Houston (2013-15) to his time in Minnesota (2016-present)? Below are images of swings by Grossman against left-handed pitchers. One is from 2015, when he was with Houston, and the other is from last season, when he was with Minnesota.

The first three images are meant to display how Grossman loaded his hands before the pitch. Notice that in the first two, from 2015, he coiled his bat significantly:

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This next image is from 2016, the first year Grossman had success against lefties. Notice that he does not coil his bat:

The next two images show how he positions himself just before the pitcher releases the ball. In first image, Grossman continues to hold his bat in a coiled position at this late stage. Also of note, his leg kick is significantly more exaggerated in the second image, which appears to put his lower half in a better power position:

The last two images show how Grossman is positioned just before the swing, when his front foot makes contact with the dirt after the leg kick. Again, in the first image, his bat remains coiled and is relatively upright. In the second image, his bat remains in its original position as well, and has a much shorter path to the ball. His lower half looks more prepared for power in the second image:

Both swings resulted in home runs. Check out video of the first swing here and the second swing here. Be sure to wait around for the slow motion replays of both swings.

The images and the videos make one thing clear: the second swing is simpler, quieter, and more explosive. At least from looking at the two swings, Grossman seems to have made an observable change to his swing from 2015 to 2016 that could, at least in part, explain his improved numbers across the board, particularly against lefties.

It would be foolish, however, to look at a couple of swings and a couple hundred plate appearances and be done with the analysis. A deeper dive into the numbers is necessary. Here’s how Grossman fared from 2013-15 compared to 2016-17:

Robbie Grossman, 2013-15 vs. 2016-17 Season Team PA BB% K% AVG OBP SLG ISO BABIP wOBA wRC+ 2013-15 HOU 764 10.9% 25.1% .240 .327 .341 .101 .320 .302 92 2016-17 MIN 452 15.3% 23.7% .283 .396 .444 .160 .366 .369 133

First things first, that’s a pretty great walk rate. According to this sample size chart, walk rates stabilize after around 120 plate appearances, so Grossman’s elite ability to draw walks should be repeatable.

The next thing that stands out is the improved power. Over his last 452 plate appearances, Grossman has raised his slugging percentage by .103 points and his ISO by .059 points. Slugging percentage normalizes after about 320 at-bats, and ISO normalizes after roughly 160 at-bats, so there seems to be a real improvement in that department as well.

Much of Grossman’s recent success, however, has been fueled by a high .366 BABIP. Before we buy into its sustainability, we need to examine what’s driving it. Below are Grossman’s batted ball numbers from 2013-15 compared to 2016-17. For context, American League average stats (pitchers excluded) are also listed for both time periods:

Robbie Grossman vs. AL Average, Batted Ball, 2013-15 vs. 2016-17 Season Player(s) LD% GB% FB% HR/FB Pull% Cent% Oppo% Soft% Med% Hard% 2013-15 Grossman 22.5% 44.6% 32.9% 7.1% 37.7% 33.0% 29.3% 17.9% 58.8% 23.3% AL (NP) 20.8% 44.0% 35.2% 10.7% 40.7% 34.6% 24.7% 17.6% 53.2% 29.3% 2016-17 Grossman 25.8% 39.5% 34.7% 12.8% 43.4% 31.8% 24.8% 17.5% 50.0% 32.5% AL (NP) 20.4% 44.0% 35.6% 12.9% 40.9% 34.1% 25.0% 18.8% 49.7% 31.5%

Surprise, surprise. Grossman, like seemingly so many others these days, has dramatically reduced his ground ball rate. While he used to hit grounders at a league-average rate, over the last 452 plate appearances he’s hit them 4.5% less often than the league average.

Despite the 5.1% cut to his ground ball rate since 2013-15, Grossman’s fly ball rate only went up by 1.8%. He made up the majority of the difference by hitting more line drives (+3.3%), and his line drive rate since 2016 is 5.4% better than the league average. Grossman has also dramatically improved his hard-hit rate, from 23.3% in 2013-15 to 32.5% in 2016-17, a 9.2% improvement.

While ground ball rates and fly ball rates stabilize after just 80 balls in play, line drive rates and BABIP require approximately 600 and 800, respectively, before they should be trusted.

Ground balls, line drives, and speed are usually what drive high batting averages on balls in play. As such, it seems that Grossman’s high line drive rate is responsible for his elevated BABIP, since he’s not a well-above-average runner and his ground ball rate is below league average. Since he hasn’t sustained his new, higher line drive rate for long enough yet, it remains to be seen if Grossman can sustain the new BABIP.

But he is well on his way. The breakout started last year, and there are numerous observable changes that suggest his recent success may be sustainable, at least to some degree. He used to be dreadful against left-handed pitching, and he solved that problem. It appears as though he changed his swing, which could explain everything. Over his last 450 plate appearances or so, his batted ball profile and outcomes have changed and improved dramatically in key areas.

From a fantasy perspective, Grossman is worth an add (especially in deeper OBP or points leagues) as a potential low-cost, above-average outfielder.