Going Deep: Making Sense of Yandy Diaz

Yandy Diaz has provided a nice surprise boost to fantasy owners in 2019, and did so especially in the season’s first month. After being traded to the Tampa Bay Rays from the Cleveland Indians in the 2018 offseason, Diaz has so far improved on an already solid 2018 campaign where he posted a .312/.375/.422 triple-slash.

Having never been much of a power threat, even in his minor-league career, Diaz’s nine home runs through just 158 PAs in 2019 tie a professional career high he previously set in 2016 in 526 PAs between AA and AAA in the Indians’ organization.

Entering Monday’s games, Diaz sported a .274 ISO, almost .150 points higher than his previous pro best, a .136 mark that also came in that 2016 AAA run. Diaz’s 139 wRC+, paired with the Rays’ continued resurgence, has helped him post 24 runs, 22 RBI and an eye-popping .541 slugging percentage.

His ground ball rate has always been higher than 50% and his GB/FB ratio is higher than 2.00 for his career. So far in May, where he has a 77 wRC+, Diaz has actually improved his hard-hit and fly-ball rates and cut down on his ground-ball rate from his March and April, when he put up a 163 wRC+.

	Hard-hit%	FB%	GB%
March/April	39	31.2	54.5
May	44.4	36.1	41.7

Diaz is an interesting case, as his elite production has cooled significantly in recent weeks, but underlying data, specifically xwOBA, suggests that his blistering start may have been lucky, while his recent downturn comes at a time when his season xwOBA has been at or near its highest.

Diaz has always had a good approach at the plate, evidenced by double-digit walk rates in every season save for a 9.2% mark in 2018 and a career 17.3% K-rate. The knock against Diaz, and likely an explanation for his lack of power up to this point in his career, has been the type of contact he makes.

Diaz has made improvements to his worm-burner tendencies for three straight seasons now, but keep in mind that he started at a place where a significant jump was going to be needed to become a reliably powerful batter. His launch angle distribution this season, while better overall, has been pretty significantly varied. Diaz’s launch angle distribution charts from the past three seasons are below, starting with 2017 at the top.

 

That, coupled with his 29.2% HR/FB rate in March and April, gives me pause about the legitimacy of his breakout. That said, the underlying numbers—hard hit rate, fly ball rate and xwOBA, in particular—are there and even stronger since his production began to tail off.

At this point in time, I likely wouldn’t want to be relying on Diaz in my starting lineup every day, but I don’t think I could bring myself to cut bait just yet. Let’s keep an eye out and see what he does over the next month.