Marcus Semien v. 2019 & 2021?

As we’re nearing the end of spring training and getting ready for the start of the regular season, one question on the minds of Blue Jays fans is: which version of Marcus Semien are we going to get? Will it be the Semien of 2019, who finished 3rd in the AL MVP race, and had a wRC+ of 138? Or will Semien’s 2021 season be more in line with his pre-2019 production, i.e. wRC+ in the 90-100 range?

To answer that question, I wanted to look at some of Semien’s underlying statistics from that 2019 season, and compare them, mostly, to his 2018 statistics. Semien had 700+ plate appearances in both of those years, which gives us comparable sample sizes. I will use the 2020 season statistics a little bit to illustrate a few tendencies, but given the overall limitations and unique challenges of 2020, I won’t rely on that unfortunate year too much.

Semien went from slashing .255/.318/.388 in 2018 up to .285/.369/.522 in 2019. Starting with the OBP, the increase – besides the 30 point jump in batting average – was also driven by Semien’s career-high walk rate of 11.6%, and career-low strikeout rate of 13.7%.

Courtesy MLB Statcast

Semien’s increased walk rate wasn’t a result of just taking more pitches – in 2018, he saw 4.098 pitches per plate appearance, while in 2019 it was 3.969/PA. Semien simply chased less out of the zone, and made more contact in the zone in 2019.

YearZ_Contact %Chase %Whiff %
Courtesy MLB Statcast

As a matter of fact, in 2019, Semien set a career high for zone contact rate, and career lows (up until 2019) for chase and whiff percentages. He was also one of only five qualified batters, who had sub-20% chase and whiff rates in 2019 (the others being Alex Bregman, Mookie Betts, Mike Trout, and Joey Votto).

The reason why I included 2020 in the table above is because it highlights two trends that will play a large role in determining what kind of a year Semien has at the plate. First: will he keep chasing less than 20% of the pitches out of the zone? Since 2016, his chase rate has been steadily declining; he didn’t expand the strike zone even after that horrendous start to the 2020 campaign. I would not be surprised to see that particular trend continue.

The second part of the equation, however, will be seeing whether the 2020 decline in zone contact is real or not. The MLB average zone contact percentage is 82.2%, and Semien dipped below that level only in 2016 and 2020. For what it’s worth, Semien’s chase contact percentage decreased only slightly from 61.2% in 2019 to 60.2%* in 2020. Nevertheless, it will be interesting to see if Semien’s zone contact rate can get back up to the mid-80s.

Turning our attention to the damage Semien does with pitches he makes contact with, his slugging percentage jumped from .388 in 2018 to .522 in 2019. The biggest contributor to that .522 slug were batted balls in the lower two-thirds of the zone.

That fact in and of itself was not new in 2019. In both 2018 and 2019, Semien did more damage when he connected with pitches in the lower part of the zone. The 2018 zone breakdown is on the left, 2019 on the right.

What did change from 2018 to 2019 was that it seems that Semien was more actively looking to swing at pitches down in the zone in 2019. We can use his swing decisions when ahead in the count as a proxy. Below are his swing rates at 1-0 and 2-0, with a minimum of 5 swings per given square in 2019:

And these are the swing decisions in one strike counts, when ahead, in 2019:

Where I think the preference for low strikes is illustrated best is in the 2-0 count box, where the hitter is really in the driver’s seat and can zero in at a particular location. In that count, in 2019, Semien was thinking “middle of the plate, down in the zone.”

Let’s contrast these with the same figures for the year 2018. First, the swing decisions with 0 strikes, minimum five swings per square:

And these are the swing decisions up ahead in the count at 2-1 and 3-1 for 2018:

Looking at the 1-0 and 2-1 counts in 2018, it seems that Semien was thinking “middle of the plate,” but was willing to swing at pitches higher in the zone as well. What I also find interesting is the different 2-0 swing profiles; in 2018, Semien was looking “middle-middle,” whereas in 2019 that became “middle-down.”

Whether or not Semien can keep hammering pitches low in the zone will be the second thing – the first being his chase and zone contact rates – worth monitoring in the 2021 season. He has traditionally had more success with pitches low, and in 2019, his swing decisions, at least when ahead in the count, played into his strength more than in 2018.

As of the evening of March 24th, Semien is slashing .256/.356/.538 in 39 spring training at-bats. An encouraging sign of his continued low strike hitting prowess was on display a few days ago in his first at-bat in a game against the Tigers.

Courtesy MLB Statcast

Semien took pitch #1, swung and missed at #2, and took #3. With the count 1-2, he got a sinker in the lower part of the zone, middle-away – right in his wheelhouse – and didn’t miss it. 102.8 mph exit velocity + 24 degree launch angle = 413 feet home run to center field. Shades of 2019, and a good sign for Blue Jays fans.

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