Jason Heyward has been on fire for the second half of May slashing .357/.406/.536 .942 OPS and 151 wRC+ since May 15. More of that please.
Been shamelessly plugging him for awhile now. His expected slash line is .284/.364/.477 for the season. The underlying numbers really are that good but the increase in fly balls he's had just aren't falling. 42.9% of his batted balls have had an exit velocity over 95. Guy immediately above him is Anthony Rendon who's hitting .263/.351/.481. Guy one spot lower than him is Yasmani Grandal who's hitting .261/.369/.471. Other names within +/- 1% of him are Lindor, Mauer, Freeman, Moustakas, Bogaerts, Asdrubal Cabrerra, Nomar Mazara, Wilson Ramos, Lowrie, Javy Baez, Schebler, Markakis, Domingo Santana, Soler, Brantley and McCann. Of all those names only 3 guys are below 115 wRC+. McCann is at 89. Santana is at 90 and Schebler is at 103. This isn't the most scientific way to do this but if you take all of their wRC+ and average them the average would be 128.4. The list has 4 guys below 120(89, 90, 103 115), 5 in the 120-129 range(123, 124 x2, 125, 128), 3 in the 130-139 range (132, 133, 135), 4 in the 140-149 range (140, 142, 144, 145) and 2 other above 150(158, 162).
In other words, the results you'd expect for how hard he's hitting it don't match what he's doing which is usually a good place to start when looking for an improvement. I'll say it again and risk looking crazy. His numbers aren't that far off Rizzo's 2017. In terms of non-batted ball data, Rizzo was at 13.2%/13.0% bb/k rate last year. Heyward is at 10.3%/11.0% this year. So less walks but likely a few more hits so you'd expect slightly better batting average and probably slightly worse OBP. In terms of batted ball data, Rizzo's LD/GB/FB split was 20.1%/40.7%/39.2%. Of the 39.2% fly balls he hit, 10.1% were infield fly balls and 16.9% were HR. With Heyward those same numbers break down to 17.1%/38.7%/44.1% with 20.4% infield fly and 4.1% HR/FB. So, the obvious take away there is Heyward is hitting fewer line drives and too many infield fly balls. That also likely accounts for a comically low 4.1% HR/FB rate. His career rate is 10.9%. But it's not for lack of Heyward hitting the ball hard. his soft/med/hard rate is 21.4%/43.8%/34.8% compared to Rizzo's 2017 rates of 19.8%/45.9%/34.4%.
Long story short, I've been saying it for awhile now but I think Heyward isn't squaring enough balls up but if and when he does watch out because that 2017 Rizzo season was a 133 wRC+ season. If Heyward starts to drive some of those pitches rather than getting under them he's hitting the ball so hard right now.